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Cycle 16 Abstract catalog (based on Phase I submissions)

Generated on:          Mon Apr  9 12:08:20 EDT 2007

 

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Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11099

Title:                           A "silver bullet" for the sources of reionization

PI:                               Marusa Bradac

PI Institution:             Stanford University

 

Recent discoveries of z>6 galaxies have given us the first glimpse of the

Universe shortly after the era of reionization. The questions arose whether

these first galaxies can be made responsible for the reionization process, and

how long did it last. Neither observations nor theory provide a clean answer.

In particular observations give results that are barely mutually consistent

and need to be further tested. Observing high redshift (z>7) sources is in

general difficult, mostly due to the high luminosity distance to these

objects, and partly due to the lower expected stellar masses compared to

objects at moderate redshifts.   We propose to use one of the most massive,

merging cluster 1E0657-56 (z=0.295) as a cosmic telescopes to efficiently

probe the high-redshift universe. The gravitational potential well of this

cluster provides several magnitudes of magnification, enabling study of

intrinsically lower luminosity galaxies.As we discuss in the proposal, due to

its highly elongated mass distribution and ideal redshift the bullet cluster

is a prime candidate for this study. We propose deep NICMOS and WFPC2

observations; with much reduced observing time compared to e.g. NICMOS UDF we

expect an order of magnitude more (~5 candidates) z>7 objects. They will also

likely be multiply imaged, and since the geometry of images depends upon the

redshift, we will be able to confirm their nature, thereby not requiring

(often prohibitive at these magnitudes) spectroscopic follow-up. This will

enable us to count high-redshift sources and constrain their luminosity

function; a task made possible with the help of gravitational lensing even in

the pre-JWST era.

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Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11100

Title:                           Two new `bullets' for MOND: revealing the properties of dark matter in massive merging clusters

PI:                               Marusa Bradac

PI Institution:             Stanford University

 

The principal objective of this proposal is to study the physical nature of

dark matter by using two, massive, newly-identified merging clusters of

galaxies. As shown by the pioneering example of the ``bullet cluster''

(1E0657-56), such systems are ideal laboratories for detecting dark matter and

distinguishing between cold dark matter (CDM) and other scenarios (e.g.  self-

interacting dark matter). Our limit on the self-interaction cross-section of

dark matter relies on the assumption of a normal pre-merger mass-to-light

ratios, and a small impact parameter during the collision of the two clusters.

In order to mitigate any possible systematic effects, it is vital to extend

this work to other, similar systems. With detailed observations of new

systems, the systematic uncertainties in the dark matter cross section

calculations can be improved substantially, allowing us to move from rough

order of magnitude estimates to measurements with quantifiable uncertainties

that can be compared usefully with the predictions from numerical simulations.

Our targets are two extraordinary, high-redshift, merging galaxy clusters

recently discovered by the Massive Cluster Survey (MACS).  This survey is by

far the best matched to this study, since it selects medium redshift (optimal

for gravitational lensing studies) and X-ray luminous (hence massive) objects.

We have selected the best candidates with clear evidence for considerable

offsets between the hot X-ray emitting gas and optically luminous stellar

material. The two most striking examples are the targets of this proposal. To

pin down the position of the dark matter component we require high resolution,

absolutely calibrated mass maps. The combination of weak and strong lensing

measurements is needed to attain this goal. This can only be achieved with the

excellent resolving power of the HST (in combination with wide-field,

multicolor Subaru data already in hand).  We therefore request multicolor

HST/WFPC2 observations of the two merging clusters. The combination of

constraints from multiply lensed images (identified via morphology and color

information) and high-resolution weak lensing data will allow us to construct,

self-consistently, their mass distribution from the very centers to the

outskirts. Gravitational lensing thus provides a unique tool transforming

these clusters into dark matter laboratories. They will supply us with answers

as to the nature and properties of dark matter, and how it shapes galaxies and

galaxy clusters and their evolution through cosmic time.

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Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11101

Title:                           The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies

PI:                               Gabriela Canalizo

PI Institution:             University of California - Riverside

 

The majority of QSOs are known to reside in centers of galaxies that look like

ellipticals. Numerical simulations have shown that remnants of galaxy mergers

often closely resemble elliptical galaxies. However, it is still strongly

debated whether the majority of QSO host galaxies are indeed the result of

relatively recent mergers or whether they are completely analogous to inactive

ellipticals to which nothing interesting has happened recently.  To address

this question, we recently obtained deep HST ACS images for five QSO host

galaxies that were classified morphologically as ellipticals (GO-10421). This

pilot study revealed striking signs of tidal interactions such as ripples,

tidal tails, and warped disks that were not detected in previous studies. Our

observations show that at least some "elliptical" QSO host galaxies are the

products of relatively recent merger events rather than old galaxies formed at

high redshift. However, the question remains whether the host galaxies of

classical QSOs are truly distinct from inactive ellipticals and whether there

is a connection between the merger events we detect and the current nuclear

activity. We must therefore place our results into a larger statistical

context. We are currently conducting an HST archival study of inactive

elliptical galaxies (AR-10941) to form a control sample. We now propose to

obtain deep HST/WFPC2 images of 13 QSOs whose host galaxies are classified as

normal ellipticals. Comparing the results for both samples will help us

determine whether classical QSOs reside in normal elliptical galaxies or not.

Our recent pilot study of five QSOs indicates that we can expect exciting

results and deep insights into the host galaxy morphology also for this larger

sample of QSOs. A statistically meaningful sample will help us determine the

true fraction of QSO hosts that suffered strong tidal interactions and thus,

whether a merger is indeed a requirement to trigger nuclear activity in the

most luminous AGNs.

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Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11102

Title:                           HST as a Jovian Climate Satellite

PI:                               Imke de Pater

PI Institution:             University of California - Berkeley

 

In the past year, there have been striking changes in Jupiter's atmosphere.

Among these are the Oval BA's change from white to red, two new dark

Disturbances in the southern hemisphere, and a 30% change (since 1997) in the

aspect ratio of the potential vorticity anomaly of the GRS (not just its

associated clouds), as we determined from high-accuracy velocities extracted

from HST images. The determination of high-accuracy velocities requires both

high-resolution imaging by HST (or flybys), and our novel adaptation of

Correlation Image Velocimetry (CIV), a technique that has far greater accuracy

than the traditional method (of identifying velocity tie-points by hand). Our

proposed observations will test the hypothesis that these changes in Jupiter

validate our 2004 prediction:        that the merger of the 3 White Ovals in 1998-

2000 would lead to climate change on Jupiter. The key is to determine, by

indirect means, the temperature at the base of  the weather layer, a quantity

that cannot be observed directly at any wavelength. The new Red Oval BA's

velocities will be used to test our finding that the color change is due to

global temperature changes. The change in the GRS's aspect ratio suggests a

large (at least 20%) change in the shear of the local velocity since 1997. The

latter can be investigated only by determining Jupiter's current zonal winds.

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Proposal Category: SNAP

Scientific Category: COSMOLOGY

ID:                               11103

Title:                           A  Snapshot Survey of The Most Massive Clusters of Galaxies

PI:                               Harald Ebeling

PI Institution:             University of Hawaii

 

We propose the continuation of our highly successful SNAPshot survey of a

sample of 125 very X-ray luminous clusters in the redshift range 0.3-0.7. As

demonstrated by the 25 snapshots obtained so far in Cycle14 and Cycle15 these

systems frequently exhibit strong gravitational lensing as well as spectacular

examples of violent galaxy interactions. The proposed observations will

provide important constraints on the cluster mass distributions, the physical

nature of galaxy-galaxy and galaxy-gas interactions in cluster cores, and a

set of optically bright, lensed galaxies for further 8-10m spectroscopy.   All

of our primary science goals require only the detection and characterisation

of high-surface-brightness features and are thus achievable even at the

reduced sensitivity of WFPC2. Because of their high redshift and thus compact

angular scale our target clusters are less adversely affected by the smaller

field of view of WFPC2 than more nearby systems. Acknowledging the broad

community interest in this sample we waive our data rights for these

observations.   Due to a clerical error at STScI our approved Cycle15 SNAP

program was barred from execution for 3 months and only 6 observations have

been performed to date - reinstating this SNAP at Cycle16 priority is of

paramount importance to reach meaningful statistics.

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Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11104

Title:                           The nature of radio transients

PI:                               Avishay Gal-Yam

PI Institution:             California Institute of Technology

 

We have conducted the first ever blind, wide-field survey for radio transients

(Levinson et al. 2002; Gal-Yam et al. 2006). We have discovered four radio

transients and explored their nature using radio and optical follow-up

observations. One is a known pulsar, one is a z~0.1 AGN, and one is most

probably an optically obscured radio supernova (SN) in the nearby galaxy NGC

4216 (the first such event to be discovered by a wide field radio survey). The

last source appears not to be associated with a bright host galaxy (to a limit

of R < 24.5 mag). We request 4 orbits of WFPC2 F606W imaging to check whether

we can establish an association between this radio transient and any of three

nearby faint resolved galaxies we have detected from the ground. If the source

is associated with any of these galaxies it would represent a new type of

extra-galactic radio bursts, more luminous than, e.g., radio afterglows of

gamma-ray bursts. Alternatively, ruling out an association with these galaxies

would disfavor an extra-galactic nature of this object, and suggest instead

that this is a radio outburst of a faint Galactic compact object, probably a

new type of radio-flaring neutron star. If this is the case, the high

luminosity (9 mJy) and relatively high galactic latitude (33 degrees) of this

source may indicate it is relatively nearby. This single source represents a

large population (comparable in sky density to AGN, pulsars, and radio SNe)

and thus merits intensive study. A modest investment of HST time, leveraged by

massive ground-based radio and optical efforts, will allow us to identify a

new class of radio sources, and complete a census of the variable radio sky

down to ~6 mJy, leaving no unidentifed objects. This result can be directly

scaled to predict the number and type of transient sources expected to be

detected by future surveys with the next generation radio arrays, such as ATA

and SKA.Since our science critically requires HST's spatial resolution (rather

than sensitivity) it is perfectly suited to be carried out with WFPC2.

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Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11105

Title:                           The LBV progenitor of SN 2005gl - a new key to massive star evolution puzzles

PI:                               Avishay Gal-Yam

PI Institution:             California Institute of Technology

 

The currently accepted theory regarding the last stages of massive star

evolution maintains that the evolution of the envelope is coupled to that of

the stellar core. For this reason, very massive stars are expected to shed

their outer hydrogen envelopes before they develop large iron cores, and

ultimately, explode as core-collapse supernovae (SNe). It is therefore a

strict prediction of current models that massive stars (certainly those above

~40 solar mass) will explode as hydrogen-poor SNe, i.e., of Types Ib and Ic.

In particular, the class of luminous blue variables (LBVs) such as eta-Carina,

which are known to be very massive (up to 100 solar masses and above) are

expected to lose their entire hydrogen envelopes prior to their ultimate

explosions as SNe. However, using pre-explosion HST/WFPC2 imaging of the

location of the recent hydrogen-rich type IIn SN 2005gl, we have identified

(Gal-Yam et al. 2007) its putative progenitor as a very luminous point source

(with absolute V magnitude of -10.2). If this is a single star, it must be an

LBV from luminosity considerations (no other stars are as luminous). If our

progenitor identification is correct, at least in some cases, massive stars

explode before losing most of their hydrogen envelope, indicating the core and

envelope are decoupled, and requiring revision of stellar evolution theory.

Here, we propose a single-orbit HST observation of the location of SN 2005gl

designed to test whether the point source we identified as its LBV progenitor

has indeed disappeared (as expected from a single star) or remained unchanged

(as expected, e.g., if it is a compact star cluster). These data are the last

observational ingredient required to firmly establish (or refute) the

explosion of an LBV as a type IIn SN, with fundamental implications for the

theory of massive star evolution. Since the new data will be compared to pre-

explosion WFPC2 images, this program is perfectly suited to be carried out

with the WFPC2 camera.

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Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11106

Title:                           Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus

PI:                               Heidi Hammel

PI Institution:             Space Science Institute

 

The planet Uranus is demonstrating increased atmospheric activity as it

approaches its 2007 equinox, perhaps in response to extreme insolation change.

Convective sites in the planet's southern hemisphere reached unprecedented

altitudes in 2003 (Hammel et al. 2005, Icarus 175, 284); a bright northern

feature showed the highest contrast yet detected in an outer planet atmosphere

(Sromovsky et al. 2007, Icarus, submitted); and a dark atmospheric feature was

detected by HST for the first time (Hammel et al. 2007, in preparation).  The

historical record makes references to discrete structures (both bright and

dark) on Uranus during previous equinoctial apparitions (the last equinox

occurred in 1965).  The best amateur facilities are now just able to resolve

the disk of Uranus and detect such activity if it is very large or has very

high contrast.  Amateurs also have access to a great many nights of telescope

time.  If a discrete cloud feature on Uranus is reported through the amateur

network, we propose to obtain follow-up images with HST's WFPC2.  The proposed

TOO images will permit determination of detailed structure of the feature at

visible wavelengths, and will provide vertical and horizontal constraints on

the feature's scattering properties.  HST is the only facility that can

provide such information at visible wavelengths.

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Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11107

Title:                           Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe

PI:                               Timothy Heckman

PI Institution:             The Johns Hopkins University

 

We have used the ultraviolet all-sky imaging survey currently being conducted

by the Galaxy Evolution Explorer (GALEX) to identify for the first time a rare

population of low-redshift starbursts with properties remarkably similar to

high-redshift Lyman Break Galaxies (LBGs). These "compact UV luminous

galaxies" (UVLGs) resemble LBGs in terms of size, SFR, surface brightness,

mass, metallicity, kinematics, dust, and color. The UVLG sample offers the

unique opportunity of investigating some very important properties of LBGs

that have remained virtually inaccessible at high redshift:      their morphology

and the mechanism that drives their star formation. Therefore, in Cycle 15 we

have imaged 7 UVLGs using ACS in order to 1) characterize their morphology and

look for signs of interactions and mergers, and 2) probe their star formation

histories over a variety of timescales. The images show a striking trend of

small-scale mergers turning large amounts of gas into vigorous starbursts (a

process referred to as dissipational or "wet" merging). Here, we propose to

complete our sample of 31 LBG analogs using the ACS/SBC F150LP (FUV) and WFPC2

F606W (R) filters in order to create a statistical sample to study the

mechanism that triggers star formation in UVLGs and its implications for the

nature of LBGs. Specifically, we will 1) study the trend between galaxy

merging and SFR in UVLGs, 2) artificially redshift the FUV images to z=1-4 and

compare morphologies with those in similarly sized samples of LBGs at the same

rest-frame wavelenghts in e.g. GOODS, UDF, and COSMOS, 3) determine the

presence and morphology of significant stellar mass in "pre-burst" stars, and

4) study their immediate environment. Together with our Spitzer (IRAC+MIPS),

GALEX, SDSS and radio data, the HST observations will form a unique union of

data that may for the first time shed light on how the earliest major episodes

of star formation in high redshift galaxies came about.  This proposal was

adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing

constraints, and can be carried out using the ACS/SBC and WFPC2 without

compromising our original science goals.

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Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11108

Title:                           Near Infrared Observations of a Sample of z~6.5-6.7 Galaxies

PI:                               Esther Hu

PI Institution:             University of Hawaii

 

The majority of the most distant galaxies discovered to date have been found

by strong Lyman alpha emission at red optical wavelengths.  An accurate

estimate of  the star formation rates for these objects requires a measurement

of the line-free UV continuum, which must be taken at infrared wavelengths.

Here we propose to obtain imaging with NICMOS in the F160W filter for a sample

of 9 Lyman alpha galaxies with redshifts z~6.5 up to z=6.740 from a complete,

flux-limited widefield narrowband and multi-color survey conducted on the 8-m

Subaru Telescope. This program will investigate galaxy morphologies and star

formation for a uniform sample of the highest redshift galaxies now known.

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Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11109

Title:                           Characterization of the UV absorption feature in asteroid (1) Ceres

PI:                               Jianyang Li

PI Institution:             University of Maryland

 

We propose to obtain the UV spectrum of asteroid (1) Ceres from 120 nm to 200

nm with ACS/SBC objective prism to characterize the broad and deep absorption

feature within this wavelength range as reported recently.  Our scientific

goals include, 1) to characterize the absorption band, 2) to determine the

origin of this spectral feature and constrain the surface compositions of

Ceres, and 3) to understand the albedo and color features on Ceres.  HST is

the only observatory currently capable of obtaining spectroscopy in this

wavelength range.  This observation will help improve our knowledge about this

largest and oldest asteroid, and support the planning of the upcoming NASA

Discovery Program mission, Dawn, orbiting asteroids Vesta and Ceres.

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Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11110

Title:                           Searching for Lyman alpha Emission from FUSE Lyman Continuum Candidates

PI:                               Stephan McCandliss

PI Institution:             The Johns Hopkins University

 

We have recently been granted time on FUSE to characterize the escape fraction

of hydrogen Lyman continuum (Lyc) photons from a morphologically diverse set

of star forming galaxies.  The FUSE program is designed to provide ~ 5 sigma

detections of  Lyc photons emitted from star forming galaxies with escape

fractions ~5%.  With this proposal we seek hydrogen Lyman alpha (Lya)

observations of a representative subset of the FUSE program targets to

constrain the observational relationship between Lyc, Lya, and hydrogen Balmer

line emission in these systems.  Such observations explore the detailed

balance between the simple optically thin (Case A) and optically thick (Case

B) limits in recombination theory.  The ultimate goal of this program is to

quantify the relationship between escaping Lya and Lyc emission and the first

structures that form in the early universe.

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Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11111

Title:                           A Search for an Intermediate Mass Black Hole in the Globular Cluster NGC 6266

PI:                               Bernard McNamara

PI Institution:             New Mexico State University

 

We propose to search for an intermediate mass black hole (IMBH) in the core of

the galactic globular cluster NGC 6266. Based on a comparison between the

observed central surface brightness profiles of 38 globular clusters and

state-of-the art N-body simultations, NGC 6266 offers the best hope of

detecting an IMBH among these objects. This detection would be significnat for

at least two reasons. It would be the first concrete discovery of an IMBH,

revealing unique information about the environment in which these objects

form, and second, its discovery would provide a powerful validation on the N-

body simultations used to track the dynamical evolution of globular clusters.

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Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11112

Title:                           The Collisional Ring Galaxy NGC922

PI:                               Gerhardt Meurer

PI Institution:             The Johns Hopkins University

 

We request WFPC2 images of the newly recognized collisional ring galaxy NGC922

which will become the nearest such system observed by HST. These will be used

to get a clear understanding of the geometry of the interaction and the

induced star formation in this system.  Quantitive modeling of the colors of

the star clusters and stellar populations will be used to constrain the star

formation history of the system.  They will also be used to test the "infant

mortality" scenario for star cluster evolution. The derived population ages

will test predictions of how star formation evolves in the various components

(ring, core, spokes) of collisional rings, and will improve our own

simulations of this system.  These will be used to determine the final fate of

the stars formed in the present burst - some will end up in a central bar or

bulge while others will become part of a thickened disk.  By analogy this will

tell us how similar collisions enrich stellar populations in the early

universe.  This is especially relevant since the number density of collisional

rings increases rapidly with redshift.

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Proposal Category: SNAP

Scientific Category: SOLAR SYSTEM

ID:                               11113

Title:                           Binaries in the Kuiper Belt:            Probes of Solar System Formation and Evolution

PI:                               Keith Noll

PI Institution:             Space Telescope Science Institute

 

The discovery of binaries in the Kuiper Belt and related small body

populations is powering a revolutionary step forward in the study of this

remote region.  Three quarters of the known binaries in the Kuiper Belt have

been discovered with HST, most by our snapshot surveys.  The statistics

derived from this work are beginning to yield surprising and unexpected

results.  We have found a strong concentration of binaries among low-

inclination Classicals, a possible size cutoff to binaries among the Centaurs,

an apparent preference for nearly equal mass binaries, and a strong increase

in the number of binaries at small separations.  We propose to continue this

successful program in Cycle 16; we expect to discover at least 13 new binary

systems, targeted to subgroups where these discoveries can have the greatest

impact.

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Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11114

Title:                           Improving proper motion measurements of  the stars in the field of SN 1572 with WFPC2

PI:                               Pilar Ruiz-Lapuente

PI Institution:             Universidad de Barcelona

 

We propose to complete the spatial velocity measurements of the stars in the

central region of the remnant of SN 1572, one of the historical Galactic Type

Ia supernovae. A new visit with WFPC2 would allow us to significantly improve

the accuracy of the proper motion measurements of the stars in the field,

since we would benefit from a long temporal baseline by using the WFPC2 images

previously taken. This unique legacy would complement the high-precision

ground-based observations made for the stars in the SN 1572 field during the

past ten years. The search for the companion star of Galactic Type Ia

supernovae, based on their high peculiar velocity as a salient feature, has

already pointed to a good candidate for SN 1572. The current uncertainties in

the tangential velocity of the candidate star and the other stars in the field

can be reduced to less than a half with a visit in Cycle 16. This would lead

to a precise determination of the parameters of the binary system that gave

rise to the supernova. If not done during Cycle 16, the long temporal baseline

for SN 1572 with WFPC2 would be lost.

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Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11115

Title:                           Photometric Imaging of Asteroid 2 Pallas

PI:                               Christopher Russell

PI Institution:             University of California - Los Angeles

 

We propose to conduct the first HST imaging of Asteroid 2 Pallas with WFPC2-PC

over 8 HST orbits.  We will image the asteroid in five filters:   F336w, F439w,

F555w, F675w and F814w.  We will utilize these observations to drastically

improve the knowledge of Pallas' shape, spin pole position and surface

properties, including roughness and albedo, parameters that are poorly

determined by previous study. These observations will result in high signal-

to-noise, high resolution surface maps from the visible to the UV.  A

satellite search will also be conducted for objects within the stability field

of up to 21st magnitude, or about 900m in diameter.  It is demonstrated in our

proposal that significant scientific opportunity exists in Cycle 16 because

Pallas is at both a low-phase, 3.9 degree opposition and near its closest

approach to Earth, conditions that do not occur simultaneously in the next

twenty years.  This window represents the best chance to answer long standing,

fundamental questions about Pallas, the main asteroid belt, and the formation

of the solar system.

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Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11116

Title:                           Exploring the Early FUV History of Cool Stars: Transition Regions at 30 Myr

PI:                               Steven Saar

PI Institution:             Smithsonian Institution Astrophysical Observatory

 

Stellar magnetic activity derives from the so-called "dynamo," a hydromagnetic

interplay between overturning plasma motions and differential rotation in

stars cool enough to support significant surface convection zones.  The

magnetic fields resulting from dynamo action are in turn are responsible for a

wide range of high-energy emissions, including the spectacular outbursts

called flares.  Dynamo powered magnetic activity is not confined solely to

stars, but also must occur, for example, in accretion disks of all

descriptions, and in some planets.  A great deal is known about magnetic

activity in middle-aged G dwarfs like our Sun, thanks to its proximity.  Less

is known, however, about the much younger stars, newly emerged from the T-

Tauri stage.  Yet, it is during this phase that they reach the peak of their

magnetic activity, and subsidiary influences, such as the impact of ionizing

radiation and strong coronal winds on developing solar systems, also are

maximum.  One of the key missing ingredients in our current understanding are

measurements of FUV emissions of such stars, to complement the extensive

collections of coronal (1-10 MK) X-ray measurements, particularly from recent

ROSAT, Chandra and XMM-Newton surveys.  We propose to conduct sensitive

ACS/SBC prism ultraviolet spectroscopy of selected fields in two young (30

Myr) Galactic clusters--IC 2391 and IC 2602--to inventory the key C IV

emission index (~0.1 MK) over a much larger and more diverse sample of coeval

objects than has been possible hitherto.  A key question is whether the FUV

emissions also suffer the "saturation" and "super-saturation" at short

rotation periods seen in coronal X-rays, or whether they continue to rise in

the fastest rotating stars.  The saturation behavior of the different

temperature regimes holds important clues to the organization of the surface

active regions on these very young stars, and should allow us to distinguish

among several competing models.

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Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11117

Title:                           The Search for Atmospheric Water in the Transiting Planet HD189733b

PI:                               David Sing

PI Institution:             CNRS, Institut d'Astrophysique de Paris

 

We propose to use the NICMOS camera to search for transit NIR signatures of

atmospheric water in HD189733b.  While water absorption bands exist in the

optical and IR, space-based NIR signatures are uniquely positioned to offer

the best chance at detection.  Using narrow band photometric filters, we will

be able to detect absorption signatures while the planet is in primary

transit.  A positive detection would be the first proof of water on an

extrasolar planet.  Furthermore, it would provide invaluable planetary

information, constraining the entire chemistry.  As a byproduct of the high

SNR required for our primary science goal, we will be able to improve on the

value of the planetary radius, a result independent of our primary science

objective.  The accurate radius estimate, together with planet structure

models, will allow constraining the planet interior and its relationship with

formation models and stellar metallicity.

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Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11118

Title:                           Investigating Near-Equinox Atmospheric Change on Uranus

PI:                               Lawrence Sromovsky

PI Institution:             University of Wisconsin - Madison

 

Uranus is approaching its 7 December 2007 equinox, when we will be able to

observe the entire northern hemisphere for the first time with modern cameras.

The large seasonal phase shift expected from its long radiative time constant

implies that it should now exhibit nearly maximal hemispheric contrast, and

should be in the process of reversing.  Many changes already observed, such as

the development of the first visible-wavelength dark spot, discovered in Cycle

15, and the fading of the south polar cap may be indicative of the expected

reversal.  We propose a detailed characterization of Uranus' current seasonal

response with a 7-orbit program consisting of 1 orbit of NICMOS imaging of

cloud bands and 6 orbits of WFPC2 imaging using both broadband and narrow-band

filters capable of tracking dark and bright discrete cloud features.  Filters

between 0.467 and 1.87 microns will provide vertical sensing depths scanning

through the pressure range where the putative methane and deeper H2S clouds

might plausibly exist and provide strong constraints on their contributions

and parent gas mixing ratios.  These observations have unique combinations of

spectral range and resolution with needed temporal and spatial resolution not

available from groundbased observations. Only HST is capable of investigating

the Uranus dark spot.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11119

Title:                           The Stellar Origins of Supernovae

PI:                               Schuyler Van Dyk

PI Institution:             Jet Propulsion Laboratory

 

Supernovae (SNe) have a profound effect on galaxies, and have been used

recently as precise cosmological probes, resulting in the discovery of the

accelerating Universe.  They are clearly very important events deserving of

intense study.  Yet, even with nearly 4000 known SNe, we know relatively

little about the stars which give rise to these powerful explosions.  The main

limitation has been the lack of spatial resolution in pre-SN imaging data.

However, since 1999 our team has been at the vanguard of directly identifying

SN progenitor stars in HST images.  From this exciting new line of study, the

emerging trend from 5 detections for Type II-Plateau SNe is that their

progenitors appear to be relatively low mass (8 to 20 Msun) red supergiants,

although more cases are needed.  Nonetheless, the nature of the progenitors of

Type Ib/c SNe, a subset of which are associated with the amazing gamma-ray

bursts, remains ambiguous.  Furthermore, we remain in the continually

embarrassing situation that we still do not yet know which progenitor systems

explode as Type Ia SNe, which are currently being used for precision

cosmology.  We propose to confirm the identities of the progenitors of 4 SNe

within 17 Mpc, which we expect to occur during Cycle 16, through ToO

observations using WFPC2/PC.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11120

Title:                           A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic Center

PI:                               Daniel Wang

PI Institution:             University of Massachusetts

 

The Galactic center (GC) is a unique site for a detailed study of a multitude

of complex astrophysical phenomena, which may be common to nuclear regions of

many galaxies. Observable at resolutions unapproachable in other galaxies, the

GC provides an unparalleled opportunity to improve our understanding of the

interrelationships of massive stars, young stellar clusters, warm and hot

ionized gases, molecular clouds, large scale magnetic fields, and black holes.

We propose the first large-scale hydrogen Paschen alpha line survey of the GC

using NICMOS on the Hubble Space Telescope. This survey will lead to a high

resolution and high sensitivity map of the Paschen alpha line emission in

addition to a map of foreground extinction, made by comparing Paschen alpha to

radio emission. This survey of the inner 75 pc of the Galaxy will provide an

unprecedented and complete search for sites of massive star formation. In

particular, we will be able to (1) uncover the distribution of young massive

stars in this region, (2) locate the surfaces of adjacent molecular clouds,

(3) determine important physical parameters of the ionized gas, (4) identify

compact and ultra-compact HII regions throughout the GC. When combined with

existing Chandra and Spitzer surveys as well as a wealth of other multi-

wavelength observations, the results will allow us to address such questions

as where and how massive stars form, how stellar clusters are disrupted, how

massive stars shape and heat the surrounding medium, and how various phases of

this medium are interspersed.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11121

Title:                           Proper Motion of the Remarkable Irradiated Jet HH399 in the Trifid Nebula

PI:                               Farhad Yusef-Zadeh

PI Institution:             Northwestern University

 

The Trifid nebula has recently been of much interest because of its

identification with a large number of massive protostars, as well as young

stellar objects. HH 399 is one of the most spectacular Herbig-Haro flows

recognized to be irradiated by the UV flux of the massive O7.5 star in the

Trifid nebula. The irradiated jet, which is propagating in a fully ionized

medium, contains numerous knots along the jet and also shows evidence for a

number of isolated knots running immediately outside the jet. Two different

HST observations of the nebula, with different scientific goals, were carried

out in 1997 and 2002, having sensitivities that differed by a factor of 10. We

performed preliminary proper motion measurements of the jet based on these

observations and discovered a continuous velocity structure of the bright

knots of about 230 km/sec. Here we propose four WFPC2 orbits to reobserve HH

399 in order to carry out accurate proper motion measurements over the full

extent of the jet, based on observations spanning more than 10 years and

having equally deep sensitivity. The proposed observations are not simply a

repeat of previous measurements, as this will be the first highly accurate

proper motion measurement of an irradiated jet based on two identical epochs

of WFPC2 observations. The observations will improve the accuracy of proper

motion measurements for HH 399 by more than a factor of five and will address

important questions beyond our preliminary result. Currently measured velocity

differences between the jet features are barely significant. The factor of 5

increase in accuracy will establish the evidence for deceleration along the

jet and the lateral motion of the jet. In addition, these measurements will

address the kinematics of individual entrained and isolated blobs of the jet

as it propagates into an HII region associated with the nebula. This is the

last opportunity to perform this experiment before WFPC2 is removed from HST.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11122

Title:                           Expanding PNe: Distances and Hydro Models

PI:                               Bruce Balick

PI Institution:             University of Washington

 

We propose to obtain repeat narrowband images of a sample of eighteen

planetary nebulae (PNe) which have HST/WFPC2 archival data spanning time

baselines of a decade.  All of these targets have previous high signal-to-

noise WFPC2/PC observations and are sufficiently nearby to have readily

detectable expansion signatures after a few years.    Our main scientific

objectives are (a) to determine precise distances to these PNe based on their

angular expansions, (b) to test detailed and highly successful hydrodynamic

models that predict nebular morphologies and expansions for subsamples of

round/elliptical and axisymmetric PNe, and (c) to monitor the proper motions

of nebular microstructures in an effort to learn more about their physical

nature and formation mechanisms.  The proposed observations will result in

high-precision distances to a healthy subsample of PNe, and from this their

expansion ages, luminosities, CSPN properties, and masses of their ionized

cores.  With good distances and our hydro models, we will be able to determine

fundamental parameters (such as nebular and central star masses, luminosity,

age).  The same images allow us to monitor the changing overall ionization

state and to search for the surprisingly non-homologous growth patterns to

bright elliptical PNe of the same sort seen by Balick & Hajian (2004) in NGC

6543.  Non-uniform growth is a sure sign of active pressure imbalances within

the nebula that require careful hydro models to understand.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11123

Title:                           A NICMOS Survey for Proplyds in the RCW 38 Massive Embedded Cluster

PI:                               Tyler Bourke

PI Institution:             Smithsonian Institution Astrophysical Observatory

 

We propose a search for line emission from photoevaporating protoplanetary

disks in the  Massive Embedded Cluster RCW 38. These disks would be analogous

to the "proplyds" discovered in the Orion Nebula:        disks around young low mass

stars which are being photoionized by a nearby O star.  We will search for

these disks in RCW 38 using narrowband imaging in the lines of Paschen alpha

and molecular hydrogen (1-0) S(1) with NICMOS.  The RCW 38 region is an

excellent target for determining whether proplyds are  observable in large

numbers outside of Orion.  It is a young embedded cluster hosting a  few

hundred low mass young stars with a large percentage showing infrared excess

indicating the presence of disks.  About 100 of these stars are found within

0.1 pc of the central O5 star, and the cluster is located within a cleared

cavity 0.2 pc in size,  embedded within a molecular cloud, exposing the

cluster members directly to the UV radiation from the O star.  Unlike Orion,

but like many other young clusters, RCW 38 is not seen in visible light, and

infrared imaging is needed.  The best line in the infrared for revealing

proplyds is the Paschen alpha line, which is not detectable from the ground.

Only HST is able to perform these observations.  From these observations we

will estimate the lifetime of the evaporating disks, and ascertain whether

these disks will survive long enough to form planets.

======================================================================

 

Proposal Category: GO

Scientific Category: QUASAR ABSORPTION LINES AND IGM

ID:                               11124

Title:                           The Origin of QSO Absorption Lines from QSOs

PI:                               David Bowen

PI Institution:             Princeton University

 

We propose using WFPC2 to image the fields of 10 redshift z ~ 0.7 foreground

(FG) QSOs which lie within ~29-151 kpc of the sightlines to high-z background

(BG) QSOs. A surprisingly high fraction of the BG QSO spectra show strong MgII

(2796,2803) absorption lines at precisely the same redshifts as the FG QSOs.

The high resolution capabilities of WFPC2 are needed to understand the origin

of these absorption systems, in two ways.  First, we wish to explore the FG

QSO environment as close as possible to the position of the BG QSO, to search

for interloping group or cluster galaxies which might be responsible for the

absorption, or irregularly shaped post-merger debris between the FG and BG QSO

which may indicate the presence of large amount of disrupted gas along a

sightline. Similarly, high resolution images are needed to search for signs of

tidal interactions between any galaxies which might be found close to the FG

QSO. Such features might provide evidence of young merging events causing the

start of QSO duty cycles and producing outflows from the central AGN. Such

winds may be responsible for the observed absorption lines.  Second, we seek

to measure the intrinsic parameters of the FG QSO host galaxy, such as

luminosity and morphology, to correlate with the properties of the MgII

absorption lines.  We wish to observe each field through the F814W filter,

close to the rest-frame B-band of the FG QSO. These blue data can reveal

enhanced star formation regions close to the nucleus of the host galaxy, which

may be indicative of galaxy mergers with the FG QSO host. The FG QSO

environment offers quite a different set of phenomena which might be

responsible for MgII absorption, providing an important comparison to studies

of MgII absorption from regular field galaxies.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11125

Title:                           The Dynamical Evolution of Globular Clusters

PI:                               Joel Bregman

PI Institution:             University of Michigan

 

Globular clusters evolve through dynamical interactions, with primordial

binaries extending the time until core collapse by up to an order of

magnitude, depending on the initial binary fraction.  These dynamical

interactions plus mass segregation causes the binary fraction to rise in the

core but fall at larger radii.  We hope to eventually test these broad

predictions by comparing them to the binary properties for globular clusters

at different states of evolution, defined by the ratio of their age to the

dynamical relaxation time at the half-light radius.  The most important

unknown aspects in the modeling process are the initial conditions of binaries

in the cluster.  Here we propose to determine the initial binary fraction as a

function of radius by studying three of the dynamically youngest globular

clusters (NGC 5053, NGC 5466, and NGC 5897).  The presence of binaries

thickens the Main Sequence in a color-magnitude diagram, which can be detected

with deep multicolor images.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11126

Title:                           Resolving the Smallest Galaxies

PI:                               Kristin Chiboucas

PI Institution:             University of Hawaii

 

An order of magnitude more dwarf galaxies are expected to inhabit the Local

Group, based on currently accepted galaxy formation models, than have been

observed.  This discrepancy has been noted in environments ranging from the

field to rich clusters, with evidence emerging that lower density regions

contain fewer dwarfs per giant than higher density regions, in further

contrast to model predictions.  One possible explanation for this involves the

effects of reionization on the forming galaxies and naturally explains both

the dearth of dwarf galaxies and the apparent environmental dependence.

However, before such theories can be fully tested, we require a better

understanding of the distribution of dwarf galaxies. Currently, there is no

complete census of the faintest dwarf galaxies in any environment.  The

discovery of the smallest and faintest dwarfs is hampered by the limitations

in detecting such faint and low surface brightness galaxies, and this is

compounded by the great difficulty in determining accurate distances to, or

ascertaining group membership for, such faint objects.  The M81 group provides

a unique means for establishing membership for galaxies in a low density

region complete to magnitudes as faint as M_R ~ -7.  With a distance modulus

of 27.8, the tip of the red giant branch (TRGB) appears at I ~ 24, just within

the reach of ground based surveys.  We currently have surveyed a 30 square

degree region around M81 with the CFHT/Megacam.  From these images we have

detected 15 new candidate dwarf galaxies.  We propose to use the HST with

WFPC2 to image these 15 galaxies in F606W and F814W bands in order to

construct a color-magnitude diagram down to I = 25.5 from which to measure

accurate TRGB distances to these candidate galaxies and determine star

formation and metallicity histories.  The overall project will provide a

survey of the dwarf galaxies in the M81 group environment with unprecedented

completeness to a limit of M_R < -7.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11127

Title:                           Mapping the nebula surrounding the enigmatic X-ray source at the center of the Vela Jr SNR

PI:                               Andrea De Luca

PI Institution:             CNR, Istituto di Astrofisica Spaziale

 

A compact X-ray source, showing nothing but steady unpulsed thermal emission,

lies close to the center of the young and nearby supernova remnant dubbed

"Vela Jr". It is a typical member of a class of enigmatic sources, supposed to

be the youngest members of the radio-quiet neutron star family. Quite

surprisingly, we discovered in ground-based optical observations a small

Halpha nebula spatially coincident with the X-ray source. Such a nebula

potentially carries very important information on the nature of the X-ray

source, which remains elusive in spite of large observational efforts. We

propose to use the WFPC2  to collect high resolution Halpha images  of the

nebula in order to resolve its structure, to understand its nature, and to

identify its connection with the X-ray source. Addressing all these points

will also have important implications for our interpretation of the compact X-

ray source and on of other objects of the same class.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11128

Title:                           Time Scales Of Bulge Formation In Nearby Galaxies

PI:                               David Fisher

PI Institution:             University of Texas at Austin

 

Traditionally, bulges are thought to fit well into galaxy formation models of

hierarchical merging. However, it is now becoming well established that many

bulges formed through internal, secular evolution of the disk rather than

through mergers. We call these objects pseudobulges.  Much is still unknown

about pseudobulges, the most pressing questions being:      How, exactly, do they

build up their mass? How long does it take? And, how many exist?  We are after

an answer to these questions. If pseudobulges form and evolve over longer

periods than the time between mergers, then a significant population of

pseudobulges is hard to explain within current galaxy formation theories. A

pseudobulge indicates that a galaxy has most likely not undergone a major

merger since the formation of the disk. The ages of pseudobulges give us an

estimate for the time scale of this quiescent evolution. We propose to use

21.4 orbits of HST time to complete UBVIH imaging on a sample of 33 nearby

galaxies that we have observed with Spitzer in the mid-IR. These data will be

used to measure spatially resolved stellar population parameters (mean stellar

age, metallicity, and star formation history); comparing ages to star

formation rates allows us to accurately constrain the time scale of

pseudobulge formation.  Our sample of bulges includes both pseudo- and

classical bulges, and evenly samples barred and unbarred galaxies. Most of our

sample is imaged, 13 have complete UBVIH coverage; we merely ask to complete

missing observations so that we may construct a uniform sample for studying

bulge formation.  We also wish to compare the stellar population parameters to

a variety of bulge and global galaxy properties including star formation

rates, dynamics, internal bulge morphology, structure from bulge-disk

decompositions, and gas content. Much of this data set is already or is being

assembled. This will allow us to derive methods of pseudobulge identification

that can be used to accurately count pseudobulges in large surveys. Aside from

our own science goals, we will present this broad set of data to the

community.  Thus, we waive proprietary periods for all observations.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11129

Title:                           The Star Formation History of the Fornax Dwarf Spheroidal Galaxy

PI:                               Enrico Held

PI Institution:             Osservatorio Astronomico di Padova

 

The Fornax dwarf spheroidal galaxy is one of the most luminous dwarf

satellites of the Milky Way.  It is unusual in many ways:          it hosts 5 globular

clusters, shows some relatively young stars, and has faint sub-structures

which have been interpreted as signs of recent interactions.  It is thus of

great interest to learn the complete star formation history (SFH) of Fornax to

establish a link between its evolutionary path and the predictions from

numerical simulations, as a test of our understanding of dwarf galaxy

evolution. Yet many questions remain open.  Is the old stellar population made

up of stars formed in a very early burst, perhaps before the epoch of

reionisation, or the result of a more continuous star formation between 13 and

9 Gyr ago ? How quickly did Fornax increase its metallicity during its initial

assembly and during subsequent episodes of star formation ?  Are accretion

episodes required to explain the age-metallicity history of Fornax ?  However,

there has never been a comprehensive study of the global SFH of the Fornax

field based on data of sufficient depth to unambiguously measure the age

mixture of the stellar populations and their spatial variation. We propose to

use the WFPC2 to obtain very deep images in several fields across the central

region of Fornax in order to reach the oldest main-sequence turnoffs. The

number of fields is determined by the need to measure the SFH over different

regions with distinct kinematics and metallicity.  The resolution achievable

with HST is crucial to answer these questions because, to derive the age

distribution of the oldest stars, we are interested in I magnitude differences

of the order 0.2 mag in crowded fields at V=24.5.  We will directly measure

the time variation in star-formation rate over the entire galaxy history, from

first stars coeval with the Milky Way halo to the youngest populations 200 Myr

ago. The combination of detailed CMD analysis with WFPC2 with our existing

metallicity and kinematic information will allow us to trace out the early

phases of its evolution.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11130

Title:                           AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II

PI:                               Luis Ho

PI Institution:             Carnegie Institution of Washington

 

The recent progress in the study of central black holes in galactic nuclei has

led to a general consensus that supermassive (10^6-10^9 solar mass) black

holes are closely connected with the formation and evolutionary history of

large galaxies, especially their bulge component.  Two outstanding issues,

however, remain unresolved.  Can central black holes form in the absence of a

bulge?  And does the mass function of central black holes extend below 10^6

solar masses?  Intermediate-mass black holes (<10^6 solar masses), if they

exist, may offer important clues to the nature of the seeds of supermassive

black holes.  Using the SDSS, our group has successfully uncovered a new

population of AGNs with intermediate-mass black holes that reside in low-

luminosity galaxies.  However, very little is known about the detailed

morphologies or structural parameters of the host galaxies themselves,

including the crucial question of whether they have bulges or not.

Surprisingly, the majority of the targets of our Cycle 14 pilot program have

structural properties similar to dwarf elliptical galaxies.  The statistics

from this initial study, however, are really too sparse to reach definitive

conclusions on this important new class of black holes.  We wish to extend

this study to a larger sample, by using the Survey mode to obtain WFPC2 F814W

images of 85 (from a parent sample of 175) AGNs with intermediate-mass black

holes selected from our final SDSS search.  We are particularly keen to

determine whether the hosts contain bulges, and if so, how the fundamental

plane properties of the host depend on the mass of their central black holes.

We will also investigate the environment of this unique class of AGNs.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11131

Title:                           Star formation at large radii in cooling flow brightest cluster galaxies

PI:                               Walter Jaffe

PI Institution:             Sterrewacht Leiden

 

We propose to take deep ACS FUV images of the bright central galaxies in two

powerful cooling flow clusters for which we have VLT UBR images, with the

object of determining whether the UV excesses we observe at large radii

(>15kpc) are caused by young stars, ultrahot (WR) stars, or an as yet unknown

source.  Current models of excess UV light at the AGN-dominated  centers of

these galaxies cannot easily be extended to large radii.  New understanding of

star formation in these clusters will be directly applicable to scenarios of

galaxy formation  in the early universe.

======================================================================

 

Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11132

Title:                           Constraining the age of the AB Dor system

PI:                               Markus Janson

PI Institution:             Max-Planck-Institut fur Astronomie, Heidelberg

 

The zero-age main sequence K-type star AB Dor, with an age of 25 to 125 Myr,

is the most active young star in the solar neighbourhood. It is part of a

quadruple system of young stars. The mass of AB Dor C,  the closest and lowest

mass companion, has been derived from  astrometric observations (with the VLA

and adaptive optics at the  VLT) to 94+-3 times the mass of Jupiter. The low

mass (close to the hydrogen burning limit) combined with the young age makes

AB Dor C a unique calibration source for evolutionary tracks for very low-mass

stars and brown dwarfs, provided that a precise age estimate can be derived

for the system. We propose to use the HST planetary camera to obtain resolved

component photometry of the M-type pre-main sequence star AB Dor Ba  and Bb in

order to derive individual spectral types and luminosities, which will enable

us to age-date the AB Dor system to better than +-20 Myr. In addition, the

observations will help to constrain the Ba/Bb orbit, and hence to derive

dynamical mass estimates as well.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11133

Title:                           Late-Time Photometry of SN 2005hk: A New Kind of Type Ia Supernova

PI:                               Saurabh Jha

PI Institution:             Rutgers the State University of New Jersey

 

Our lack of understanding of Type Ia supernova (SN Ia) explosions limits our

confidence in their use for cosmology.  While there is broad agreement that

these objects represent the explosions of white dwarfs, the details of the

explosion mechanism are not well-understood.  Recent observations have

detected a previously unacknowledged variant class of SNe Ia whose photometric

and spectroscopic peculiarities make them quite distinct from normal SNe Ia.

These objects represent a challenge for thermonuclear supernova models, as a

complete theory of exploding white dwarfs must allow for their existence.  A

particularly well-studied example of this class of objects is the recent SN

2005hk, whose properties in some respects resemble those of models which

invoke a subsonic burning front, called a deflagration.  We propose to test SN

Ia models by obtaining late-time photometry for this extreme SN Ia using WFPC2

and NICMOS on HST.  We will accurately measure the late-time photometric

decline rate and spectral energy distribution (SED).  These observations will

allow us to test whether the ejecta contain the large amount of oxygen

predicted by certain models, the efficiency of energy deposition by gamma rays

and positrons, and possibly detect major evolution of the SED expected due to

a change in the dominant cooling mechanism of the ejecta.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11134

Title:                           WFPC2 Tidal Tail Survey:  Probing Star Cluster Formation on the Edge

PI:                               Karen Knierman

PI Institution:             University of Arizona

 

The spectacular HST images of the interiors of merging galaxies such as the

Antennae and NGC 7252 have revealed rich and diverse populations of star

clusters created over the course of the interaction.  Intriguingly, our WFPC2

study of tidal tails in these and other interacting pairs has shown that star

cluster birth in the tails does not follow a similarly straightforward

evolution.  In fact, cluster formation in these relatively sparse environments

is not guaranteed -- only one of six tails in our initial study showed

evidence for a significant population of young star clusters.  The tail

environment thus offers the opportunity to probe star cluster formation on the

edge of the physical parameter space (e.g., of stellar and gas mass, density,

and pressure) that permits it to occur.  We propose to signficantly extend our

pilot sample of optically bright, gas-rich tidal tails by a factor of 4 in

number to include a more diverse population of tails, encompassing major and

minor mergers, gas-rich and gas-poor tails, as well as early, late, and merged

interaction stages. With 21 orbits of HST WFPC2 imaging in the F606W and F814W

filters, we can identify, roughly age-date, and measure sizes of star clusters

to determine what physical parameters affect star cluster formation.  WFPC2

imaging has been used effectively in our initial study of four mergers, and it

will be possible in this program to reach similar limits of Mv=-8.5 for each

of 16 more tails.  With the much larger sample we expect to isolate which

factors, such as merger stage, HI content, and merger mass ratio, drive the

formation of star clusters.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11135

Title:                           Extreme makeovers: Tracing the transformation of massive galaxies at z~2.5

PI:                               Mariska Kriek

PI Institution:             Universiteit Leiden

 

To obtain a full spectroscopic census of the universe at z~2.5 we have

conducted a near-infrared spectroscopic survey for K-selected galaxies.  We

found that, in contrast to the local universe, massive high-redshift galaxies

span a wide range of properties, varying from (dusty) star burst to "red and

dead" galaxies. This may imply that massive galaxies transform from star-

forming to quiescent galaxies in the targeted redshift range. To understand

whether the 9 quiescent galaxies in our sample are the progenitors of local

elliptical, we are observing them in the current cycle with NIC2.  For cycle

16 we propose to complete our sample of massive z~2.5 galaxies and image the

remaining 10 galaxies, which all have emission lines. Based on emission-line

diagnostics, 6 of these galaxies are identified as star-forming objects and 4

harbor an active galactic nucleus. The goals are to 1) determine whether star

formation in massive z~2.5 galaxies takes place in disks or is triggered by

merger activity, 2) derive the contribution of AGNs to the rest-frame optical

emission, and 3) test whether the morphologies are consistent with the idea

that the star-forming galaxies, AGNs, and quiescent galaxies represent

subsequent phases of an evolutionary sequence. The combination of both

programs will provide the first morphological study of a spectroscopically

confirmed massive galaxy sample at z~2.5.

======================================================================

 

Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11136

Title:                           Resolving Ultracool Astrophysics with Brown Dwarf Binaries

PI:                               Michael Liu

PI Institution:             University of Hawaii

 

We propose to obtain resolved far-red and near-IR photometry of 14 brown dwarf

binaries with HST/NICMOS in order to study one of the long-standing puzzles in

ultracool astrophysics, namely the rapid change in spectra from L dwarfs to T

dwarfs at nearly constant effective temperature (a.k.a. the ``L/T

transition'').  While many nearby brown dwarfs have been studied, use of such

samples is inevitably hindered by the unknown ages, masses, and metallicities

of the field population.  Characterization of resolved ultracool binaries is a

promising avenue for addressing this problem, by providing coeval systems of

the same composition with comparable masses and temperatures.  Our proposed

HST/NICMOS (0.9-1.6 micron) observations will be combined with longer

wavelength ground-based photometry and spectroscopy from Keck laser guide star

adaptive optics.  The resulting multi-band (0.9-2.5 micron) dataset will be a

unique resource for measuring the evolution of spectral energy distributions

across the L/T transition, to test state-of-the-art atmospheric models, and to

determine the physical process(es) that dominate the L/T transition.

Understanding the L/T transition is important not only for testing brown dwarf

atmospheres, but also provides a key pathway for understanding the same

physical effects, namely the formation and removal of clouds, in the

atmospheres of the extrasolar planets.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11137

Title:                           First Accurate Geometric Distance to a Galactic Wolf-Rayet Star: Knots in the Ejecta M1-67

PI:                               Anthony Moffat

PI Institution:             Universite de Montreal

 

M 1-67 is the youngest known ejection nebula surrounding a Population I Wolf-

Rayet star, in this case the WN8 star WR 124.  Our deep H-alpha HST/WFPC2

image of this object in March 1997 revealed, for the first time in such a

nebula, numerous bright, mostly unresolved knots (typical diameters 0.1-0.2")

often surrounded by what appear to be their own local spherical diffuse 'wind'

bubbles. We propose to obtain a second epoch H-alpha image of M 1-67,

essentially repeating the Epoch1 instrumental set-up. By measuring the proper

motions of the knots, we  will derive a relatively precise and assumption-free

geometric distance (thus also a  luminosity) to a Galactic   Wolf-Rayet star,

the first of its kind. This will help to confirm the suspected runaway status

of WR 124 and shed new light on the nature of progenitors of  gamma-ray

bursts. Moreover, we intend to document and measure the anticipated

morphology/brightness changes in the fine-stucture features of the nebula over

the 11-year interval, as they relate to wind-embedded shocks. This will

provide important input for interaction models of a stellar wind with

circumstellar matter.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11138

Title:                           The Physics of the Jets of Powerful Radio Galaxies and Quasars

PI:                               Eric Perlman

PI Institution:             Florida Institute of Technology

 

We propose to obtain HST polarimetry of the jets of the quasars 1150+497 and

PKS 1136-135.  Our goal is to solve the riddle of their high-energy emission

mechanism, and tackle issues such as particle acceleration and jet dynamics.

Our targets are the optically brightest quasar jets, and they span the range

of luminosities and beaming parameters seen in these objects.  Recent

observations with Spitzer, HST and Chandra have shed new light on the spectral

morphology of quasar jets, throwing wide open the question of the nature of

their optical and X-ray emission.  Three mechanisms are possible, including

synchrotron emission as well as two Comptonization processes.  Polarimetry can

uniquely determine which of these mechanisms operates in the optical.  We will

compare the optical polarimetry to in-hand radio polarimetry as well as in-

hand and new Spitzer, HST and Chandra imaging to gain new insights on the

structure of these jets, as well as particle acceleration mechanisms and jet

dynamics.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11139

Title:                           NICMOS Observations of the Microquasar GRS 1758-258

PI:                               Ian Smith

PI Institution:             Rice University

 

The galactic black hole candidate GRS 1758-258 is normally one of the

brightest persistent gamma-ray sources in the vicinity of the galactic center.

It is a microquasar with relativistic radio jets emanating from a central

variable source.  Microquasars are excellent nearby test laboratories for

studying the complex accretion and outflow processes that take place near

black hole horizons.  Despite an accurate location provided by Chandra and the

VLA and over a decade of careful ground-based studies, the optical/infrared

counterpart to GRS 1758-258 remains unknown. A stellar counterpart is

expected, but the current candidates are all more than 2 sigma from the center

of the error circle.  The ground-based infrared flux limits are also right at

the values expected for the synchrotron emission from the outflow from the

black hole, and possibly for the emission from the accretion disk. This leaves

open the question as to what is powering this very energetic persistent

source.  Here we propose to use NICMOS to perform broad-band imaging of the

GRS 1758-258 error box.  These images will be more than three magnitudes more

sensitive than the current ground-based ones. The resulting spectra will

reveal the thermal/non-thermal nature of the sources in the region of the

error box, and the high spatial resolution images may reveal a jet structure.

We propose to perform three visits of two orbits each spanning the suggested

18.45 day binary orbital period of the system:   a correct counterpart

identification should be confirmed by its variability.  We will also aim to

support the HST observations with X- and gamma-ray observations using Swift or

INTEGRAL, and with longer wavelength observations from the ground.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11140

Title:                           Can mass-ejections from late He-shell flash stars constrain convective/reactive flow modeling of stellar interiors?

PI:                               Klaus Werner

PI Institution:             Universitat Tubingen, Institut fur Astronomie & Astrophysik

 

The existence of H-deficient knots around the central stars of the planetary

nebulae Abell 30 and Abell 78 is still unexplained. We hypothesize that these

knots were ejected during a very late helium-shell flash (= very late thermal

pulse, VLTP) suffered by the precursor white dwarf stars. If this is true,

then the characteristics of these knots (mass, velocity, density, spatial

distribution) allow to draw conclusions on the course of the hydrogen-

ingestion flash detonation that is triggered by the He-shell flash. This

provides important, otherwise inaccessible constraints for the hydrodynamical

modeling of convective/reactive flows in stellar interiors. Understanding the

physics of these flows is not only important for the understanding of these

particular central stars, but also for the frequent, very similar

convective/reactive events that determine the nucleosynthesis in Pop. III

stars.  With this proposal we want to proof or discard the idea that the H-

deficient knots are resulting from a VLTP. If true, then they can be exploited

for flash-physics diagnostics. We propose a simple test. We search for such

knots around five H-deficient central stars (PG1159 stars). Our models

predict, that only those stars with residual nitrogen in the atmosphere have

suffered a VLTP and, hence, should have expelled knots. We therefore want to

take [O III] images of stars which have photospheric N and those which do not.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11141

Title:                           White dwarfs in the open star cluster NGC 188

PI:                               Kurtis Williams

PI Institution:             University of Texas at Austin

 

White dwarf cooling sequences represent the only ways in which we can

determine ages of Galactic components such as the disk and the halo, and they

are an independent check on main sequence ages of  globular star clusters.

These age measurements rely heavily on theoretical cooling models, many of

which disagree by as much as a few gigayears for the coolest white dwarfs.

Further, observations of the white dwarf sequence in the super metal-rich open

cluster NGC 6791 have found a white dwarf age several gigayears younger than

the accepted cluster age determined by main-sequence fitting.  The white dwarf

sequence of the solar-metallicity, 7-Gyr old open cluster NGC 188 can provide

some much-needed insight into these uncertainties, but previous HST

observations were too shallow to detect the oldest, faintest white dwarfs in

the cluster.  We propose deep imaging of two fields at the center of the

cluster with the following goals:    (1) To detect the end of the white dwarf

cooling sequence, providing a much-needed empirical data point for cool white

dwarf evolutionary models, (2) to compare the white dwarf luminosity function

of NGC 188 with that of NGC 6791 to determine if the odd white dwarf sequence

in the latter cluster is due to the cluster's high metallicity or due to a

shortcoming in theoretical models, and (3) to determine via photometry the

masses of white dwarfs formed by solar-mass stars, a quantity not yet

empirically measured.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11142

Title:                           Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3<z<2.7 Using HST and Spitzer

PI:                               Lin Yan

PI Institution:             California Institute of Technology

 

We aim to determine physical properties of IR luminous galaxies at 0.3<z<2.7

by requesting coordinated HST/NIC2 and MIPS 70um observations of a unique,

24um flux-limited sample with complete Spitzer mid-IR spectroscopy. The 150

sources investigated in this program have S(24um) > 0.8mJy and their mid-IR

spectra have already provided the majority targets with spectroscopic

redshifts (0.3<z<2.7). The proposed 150~orbits of NIC2 and 66~hours of MIPS

70um will provide the physical measurements of the light distribution at the

rest-frame ~8000A and better estimates of the bolometric luminosity. Combining

these parameters together with the rich suite of spectral diagnostics from the

mid-IR spectra, we will (1) measure how common mergers are among LIRGs and

ULIRGs at 0.3<z<2.7, and establish if major mergers are the drivers of z>1

ULIRGs, as in the local Universe. (2) study the co-evolution of star formation

and blackhole accretion by investigating the relations between the fraction of

starburst/AGN measured from mid-IR spectra vs. HST morphologies, L(bol) and z.

(3) obtain the current best estimates of the far-IR emission, thus L(bol) for

this sample, and establish if the relative contribtuion of mid-to-far IR dust

emission is correlated with morphology (resolved vs. unresolved).

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11143

Title:                           NICMOS imaging of submillimeter galaxies with CO and PAH redshifts

PI:                               Andrew Baker

PI Institution:             Rutgers the State University of New Jersey

 

We propose to obtain F110W and F160W imaging of 10 z~2.4 submillimeter

galaxies (SMGs) whose optical redshifts have been confirmed by the detection

of millimeter CO and/or mid-infrared PAH emission.  With the 4000A break

falling within/between the two imaging filters, we will be able to study these

sources' spatially resolved stellar populations (modulo extinction) in the

rest-frame optical.  SMGs' large luminosities appear to be due largely to

merger-triggered starbursts; high-resolution NICMOS imaging will help us

understand the stellar masses, mass ratios, and other properties of the merger

progenitors, valuable information in the effort to model the mass assembly

history of the universe.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11144

Title:                           Building on the Significant NICMOS Investment in GOODS: A Bright, Wide-Area Search for z>=7 Galaxies

PI:                               Rychard Bouwens

PI Institution:             University of California - Santa Cruz

 

One of the most exciting frontiers in observational cosmology has been to

trace the buildup and evolution of galaxies from very early times.  While

hierarchical theory teaches us that star formation in galaxies likely starts

out small and builds up gradually, only recently has it been possible to see

evidence for this observationally through the evolution of the LF from z~6 to

z~3.  Establishing that this build up occurs from even earlier times (z~7-8)

has been difficult, however, due to the small size of current high-redshift

z~7-8 samples -- now numbering in the range of  ~4-10 sources.  Expanding the

size of these samples is paramount, if we are to push current studies of

galaxy buildup back to even earlier times.  Fortunately, we should soon be

able to do so, thanks to ~50 arcmin**2 of deep (26.9 AB mag at 5 sigma) NICMOS

1.6 micron data that will be available over the two ACS GOODS fields as a

result of one recent 180-orbit ACS backup program and a smaller program.

These data will nearly triple the deep near-IR imaging currently available

over these fields and therefore represent a significant resource for finding

and characterizing the brightest and likely most massive high-redshift sources

(which can be found in no other way but with wide-area searches).  To make

maximal use of these data, we will first isolate a small sample of the most

interesting, candidate z>=7 galaxies from this survey through their z-H

colours.   We then propose to follow-up each of these candidates with NICMOS

imaging at 1.1 microns ('J'-band) to determine which of these sources are at

z>=7 and thus significantly expand our sample of luminous, z>=7 galaxies.

Since preliminary studies indicate that these candidates occur in only 30% of

the NIC3 fields, our follow-up strategy is ~3 times as efficient as without

this preselection and 9 times as efficient as a search in a field with no pre-

existing data.  We expect to identify ~8 luminous z-dropouts and possibly ~2

z~10 J-dropouts as a result of this program, more than tripling the number

currently known.  The increased sample sizes are important if we are to

solidify current conclusions about galaxy buildup and the evolution of the LF

from z~8.  In addition to the high redshift science, these deep 1.1 micron

data would have significant value for many diverse endeavors, including (1)

improving our constraints on the stellar mass density at z~7-10 and (2)

doubling the number of galaxies at z~6 for which we can estimate dust

obscuration.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11145

Title:                           Probing the Planet Forming Region of T Tauri Stars in Chamaeleon

PI:                               Nuria Calvet

PI Institution:             University of Michigan

 

By studying the inner, planet-forming regions of circumstellar disks around

low-mass pre-main sequence stars we can refine theories of giant planet

formation and develop timescales for the evolution of disks and their planets.

Spitzer infrared observations of T Tauri stars in the Chamaeleon star-forming

region have given us an unprecedented look at dust evolution in young objects.

However, despite this ground breaking progress in studying the dust in young

disks, the gas properties of the inner disk remain essentially unknown.  Using

ACS on HST, we propose to measure the H_2  emission originating in the

innermost disk regions of classical T Tauri stars in different stages of

evolution with the objective of revealing the timescales of gas dissipation

and its relationship to dust evolution.  This proposal is part of a

comprehensive effort with approved programs on Spitzer, Gemini, and Magellan

that aim to characterize the state of gas and dust in disks where planets may

already have formed.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11146

Title:                           The Role of Stellar Feedback in Galaxy Evolution

PI:                               Daniela Calzetti

PI Institution:             University of Massachusetts

 

Stellar feedback - the return of mass and energy from star formation to the

interstellar medium - is one of the primary engines of galaxy evolution. Yet,

the observational canvass of feedback is incomplete. We propose to investigate

this fundamental aspect of star formation on one local actively star-forming

galaxy, He2-10,  selected to occupy an unexplored niche in the key parameter

space of stellar mass.  The WFPC2 narrow-band observations in the light of H-

beta, [OIII], H-alpha, and [SII] will: (1) discriminate the feedback-induced

shock fronts from the photoionized regions; (2) map, and provide a complete

census of, the shocks inside and around the starburst regions; and (3) measure

the energy budget of the star-formation-produced shocks. These observations,

joined by our previous data and studies on starbursts, will yield:      (1) the

efficiency of the feedback, i.e. the fraction of the star formation's

mechanical energy transported out of the starburst volume rather than radiated

away, in the dual-parameter space of host's stellar mass and star formation

intensity; (2) the conditions under which feedback morphs from a localized

process to a galactic scale mechanism. The high angular resolution of HST is

crucial for separating the spatially narrow shock fronts (~10 pc=0.2" at 10

Mpc) from the more extended photoionization fronts. This project  will provide

the most comprehensive quantitative foundation of stellar feedback and a gauge

for determining the role of feedback in the energetics, structure and star

formation history of galaxies.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11147

Title:                           The Origin of Diffuse UV Light from Spiral Disks

PI:                               Rupali Chandar

PI Institution:             Carnegie Institution of Washington

 

The ultraviolet light from galaxies has been used as a beacon for tracing the

cosmic star formation history of the Universe, yet we have an incomplete

understandingof many characteristics of this light.  Most of the UV emission

from nearby, normal star--forming galaxies is unresolved and "diffuse", and

GALEX has shown that in spiral disks it permeates the inter-arm regions.  The

nature of this diffuse inter-arm component is under debate.  Recent results

suggest that it may arise from non-ionizing UV photons which originate in star

forming regions in the spiral arms, travel in the plane of the galaxy, and

then scatter off of diffusely distributed cold dust grains.  Alternatively, an

in-situ, unresolved stellar population could produce the observed inter-arm UV

emission.  This project seeks to establish which of the two competing

scenarios is responsible for the bulk of this diffuse emission.  We propose to

use HST's UV imaging capability (ACS/SBC) to obtain deep observations of

selected fields in the nearby spiral galaxy M101, for which available (low

angular resolution) data favor the 'scattered light' scenario.  Our

observations are designed to detect any faint, UV-luminous stellar population

down to main sequence B5 stars.  With these data, we will establish the nature

of the bulk of the diffuse UV light in this spiral galaxy by:        (i) quantifying

the contribution from dust-scattered light; (ii) measuring the contribution to

the ubiquitous diffuse ionized medium from in-situ ionizing stars; and (iii)

providing constraints on the observed stellar mass function in the field.

Only HST has the UV sensitivity and angular resolution to discriminate in-situ

stellar populations from scattered light.  The ultimate goal of this project

is to re-'calibrate' the UV emission as a star formation rate indicator, which

will need to account for any scattered component.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11148

Title:                           High Contrast Imaging of Dusty White Dwarfs

PI:                               John Debes

PI Institution:             Carnegie Institution of Washington

 

For the past 18 years, only one white dwarf with a circumstellar dust disk was

known to exist.  In the last two years, six new disks have been discovered.

Since all material inwards of a few AU should be scoured clean during post

main sequence evolution, the primary explanation is the presence of a

planetary system that is perturbing relic planetesimals into the tidal

disruption radius of the white dwarf.  Dusty disks around white dwarfs should

be markers for planets and we propose to use high contrast imaging to search

for faint companions down to 6 M_$J$ that may be feeding the disks.  White

dwarfs are uniquely suited for planet searches, where the planet/white dwarf

contrast is less than for main sequence stars.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11149

Title:                           Characterizing the Stellar Populations in Lyman-Alpha Emitters and Lyman Break Galaxies at 5.7<z<7 in the Subaru Deep Field

PI:                               Eiichi Egami

PI Institution:             University of Arizona

 

The epoch of reionization marks a major phase transition of the Universe,

during which the intergalactic space became transparent to UV photons.

Determining when this occurred and the physical processes involved represents

the latest frontier in observational cosmology. Over the last few years,

searches have intensified to identify the population of high-redshift (z>6)

galaxies that might be responsible for this process, but the progress is

hampered partly by the difficulty of obtaining physical information (stellar

mass, age, star formation rate/history) for individual sources. This is

because the number of z>6 galaxies that have both secure spectroscopic

redshifts and high-quality infrared photometry (especially with Spitzer/IRAC)

is still fairly small. Considering that only several photometric points are

available per source, and that many model SEDs are highly degenerate, it is

crucial to obtain as many observational constraints as possible for each

source to ensure the validity of SED modeling. To better understand the

physical properties of high-redshift galaxies, we propose here to conduct

HST/NICMOS (72 orbits) and Spitzer/IRAC (102 hours) imaging of

spectroscopically confirmed, bright (z<26 mag (AB)) Ly-alpha emitters (LAEs)

and Lyman-break galaxies (LBGs) at 5.7<z<7 selected from the Subaru Deep

Field. Spectroscopic redshifts remove one critical free parameter from SED

modeling while bright source magnitudes ensure high-quality photometric data.

By making accurate determinations of stellar masses, ages, and star-formation

histories, we will specifically address the following major questions:           (1) Do

LAEs and LBGs represent physically different galaxy populations at z>6 as

suggested recently? (2) Is Ly-alpha emission systematically suppressed at z>6

with respect to continuum emission? (i.e., are we reaching the epoch of

incomplete reionization?), and (3) Do we see any sign of abnormally young

stellar population in any of the z>6 galaxies?

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11150

Title:                           Beta Pic Polarimetry with NICMOS

PI:                               James Graham

PI Institution:             University of California - Berkeley

 

Debris disk stars host transient dust grains that comprise a collisional

cascade with sizes ranging from planetesimals to the sub-micron. In addition

to the gravity of the host star and any planets present, these grains are

subject to size-dependent non-gravitational forces, e.g., corpuscular drag and

radiation pressure. When a steep spectrum of grain sizes prevails, such as the

Dohnanyi distribution, scattered light images preferentially trace grains with

dimensionless size parameter of order unity. Thus images in scattered

starlight provide unique windows on the balance of forces acting on grains at

a specific size. Therefore, in an A star system such as beta Pic, the near-IR

is dominated by grains close to the blow out size and therefore NICMOS traces

dust on hyperbolic orbits.  Scattering is fundamentally polarization

sensitive, and measurements that record intensity literally see only half the

picture. If linear polarization is measured then the elements of the complex

scattering matrix can be reconstructed. These matrix elements provide

fundamental constraints on the size, composition and structure of the

scatterers. Notably, polarimetry can be used to break the degeneracy between

scattering asymmetry, g, and the radial dust gradient, which are otherwise

covariant in an edge-on disk. Thus, we can use polarimetry to localize the

parent bodies in the beta Pic disk.  In beta Pic, dust is thought to originate

mainly from the sublimation of cometary bodies near periastron. The

irradiation of cometary material leads to sublimation and photodissociation of

ices forming porous grains consisting of a matrix of refractory material. Such

grains have a characteristic scattering signature in polarized light that can

be distinguished from compact grains that arise from collisional erosion of

asteroidal material.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11151

Title:                           Evaluating the Role of Photoevaporation of Protoplanetary Disk Dispersal

PI:                               Gregory Herczeg

PI Institution:             California Institute of Technology

 

Emission produced by accretion onto the central star leads to

photoevaporation, which may play a fundamental role in disk dispersal.  Models

of disk photoevaporation by the central star are challenged by two potential

problems:      the emission produced by accretion will be substantially weaker for

low-mass stars, and photoevaporation must continue as accretion slows.

Existing FUV spectra of CTTSs are biased to solar-mass stars with high

accretion rates, and are therefore insufficient to address these problems.  We

propose use HST/ACS SBC PR130L to obtain FUV spectra of WTTSs and of CTTSs at

low masses and mass accretion rates to provide crucial data to evaluate

photoevaporation models.  We will estimate the FUV and EUV luminosities of

low-mass CTTSs with small mass accretion rates, CTTSs with transition disks

and slowed accretion, and of magnetically-active WTTSs.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11152

Title:                           Probing the compact dust disk of a nearby Classical T Tauri Star

PI:                               Bruce Macintosh

PI Institution:             Lawrence Livermore National Laboratory

 

BP Psc is a high Galactic latitude (b = -57), bright, IRAS source that

generally has been classified as a T Tauri star but little studied to date. We

have carried out a multiwavelength ground-based study of this object and find

that it is most likely a ~10 Myr classical T Tauri star surrounded by  a gas

and dust disk, and less than 100 pc from Earth, making it one of the oldest

and closest such stars known. Near-IR AO images and IR photometry show it is

surrounded by an compact (0.2"), almost-edge-on,  optically thick disk of dust

with a wide range of temperatures. We propose a multiwavelength polarimetric

study of the compact disk to support quantitative modeling to recover disk and

dust parameters. We also propose coronagraphic imaging to search for larger-

scale dust structures invisible in ground-based images, and narrowband imaging

of an outflow jet and associated Herbig-Haro objects to study their structure

and determine a kinematic distance of the system. A massive compact disk

surrounding an isolated 10 Myr star is a unique environment for planet

formation, and its proximity to Earth allows HST to study it in detail.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11153

Title:                           The Physical Nature and Age of Lyman Alpha Galaxies

PI:                               Sangeeta Malhotra

PI Institution:             Arizona State University

 

In the simplest scenario, strong Lyman alpha emission from high redshift

galaxies would indicate that stellar populations younger than 10 Myrs dominate

the UV. This does not, however, constrain the stellar populations older than

100 Myrs, which do not contribute to UV light.  Also, the Lyman alpha line can

be boosted if the interstellar medium is both clumpy and dusty.  Different

studies with small samples have reached different conclusions about the

presence of dust and old stellar populations in Lyman alpha emitters.  We

propose HST-NICMOS and Spitzer-IRAC photometry of  35 Lyman-alpha galaxies at

redshift 4.5<z<6.5, in order to determine their spectral energy distribution

(SED) extending through rest-frame optical. This will allow us to measure

accurately (1) The total stellar mass in these objects, including old stars

which may have formed at redshifts (z > 8) not easily probed by any other

means.  (2) The dust extinction in the rest-frame UV, and therefore a

correction to their present star-formation rates.  Taken together, these two

quantities will yield the star-formation histories of Lyman alpha galaxies,

which form fully half of the known galaxies at z=4-6. They will tell us

whether these are young or old galaxies by straddling the 4000A break.  Data

from NICMOS is essential for these compact and faint (i=25-26th magnitude AB)

high redshift galaxies, which are too faint for good near-IR photometry from

the ground.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11154

Title:                           Optical-UV Spectrum of the Middle-aged Pulsar B1055-52

PI:                               George Pavlov

PI Institution:             The Pennsylvania State University

 

The middle-aged radio, X-ray and gamma-ray pulsar B1055-52 is one of the few

pulsars that allow a multiwavelength study of pulsar radiation. An optical

counterpart of the pulsar has been detected with the HST FOC, but it was

observed in only one filter (F342W, m=24.9). To understand the nature of the

pulsar radiation, its spectrum must be measured in a broad wavelegth range. We

propose imaging observations of the pulsar's counterpart with  WFPC2 in the

red part of the spectrum and ACS/SBC in the UV part to measure the broadband

spectral distribution, compare it with the X-ray spectrum, and investigate the

thermal and magnetospheric components of the pulsar's radiation.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11155

Title:                           Dust Grain Evolution in Herbig Ae Stars:            NICMOS Coronagraphic Imaging and Polarimetry

PI:                               Marshall Perrin

PI Institution:             University of California - Berkeley

 

We propose to take advantage of the sensitive coronagraphic capabilities of

NICMOS to obtain multiwavelength coronagraphic imaging and polarimetry of

primordial dust disks around young intermediate-mass stars (Herbig Ae stars),

in order to advance our understanding of how dust grains are assembled into

larger bodies.  Because the polarization of scattered light is strongly

dependent on scattering particle size and composition, coronagraphic imaging

polarimetry with NICMOS provides a uniquely powerful tool for measuring grain

properties in spatially resolved circumstellar disks.  It is widely believed

that planets form via the gradual accretion of planetesimals in gas-rich,

dusty circumstellar disks, but the connection between this suspected process

and the circumstellar disks that we can now observe around other stars remains

very uncertain.  Our proposed observations, together with powerful 3-D

radiative transfer codes, will enable us to quantitatively determine dust

grain properties as a function of location within disks, and thus to test

whether dust grains around young stars are in fact growing in size during the

putative planet-formation epoch.  HST imaging polarimetry of Herbig Ae stars

will complement and extend existing polarimetric studies of disks around

lower-mass T Tauri stars and debris disks around older main-sequence stars.

When combined with these previous studies, the proposed research will help us

establish the influence of stellar mass on the growth of dust grains into

larger planetesimals, and ultimately to planets.  Our results will also let us

calibrate models of the thermal emission from these disks, a critical need for

validating the properties of more distant disks inferred on the basis of

spectral information alone.

======================================================================

 

Proposal Category: SNAP

Scientific Category: SOLAR SYSTEM

ID:                               11156

Title:                           Monitoring Active Atmospheres on Uranus and Neptune

PI:                               Kathy Rages

PI Institution:             SETI Institute

 

We propose Snapshot observations of Uranus and Neptune to monitor changes in

their atmospheres on time scales of weeks and months.  Uranus equinox is only

months away, in December 2007.  Hubble Space Telescope observations during the

past several years (Hammel et al. 2005, Icarus 175, 284 and references

therein) have revealed strongly wavelength-dependent latitudinal structure,

the presence of numerous visible-wavelength cloud features in the northern

hemisphere, at least one very long-lived discrete cloud in the southern

hemisphere, and in 2006 the first dark spot ever seen on Uranus.  Long-term

ground-based observations (Lockwood and Jerzekiewicz, 2006, Icarus 180, 442;

Hammel and Lockwood 2007, Icarus 186, 291) reveal seasonal brightness changes

whose origins are not well understood. Recent near-IR images of Neptune

obtained using adaptive optics on the Keck Telescope, together with HST

observations (Sromovsky et al. 2003, Icarus 163, 256 and references therein)

which include previous Snapshot programs (GO 8634, 10170, 10534) show a

general increase in activity at south temperate latitudes until 2004, when

Neptune returned to a rather Voyager-like appearance.  Further Snapshot

observations of these two dynamic planets will elucidate the nature of long-

term changes in their zonal atmospheric bands and clarify the processes of

formation, evolution, and dissipation of discrete albedo features.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11157

Title:                           NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum

PI:                               Joseph Rhee

PI Institution:             University of California - Los Angeles

 

Association of planetary systems with dusty debris disks is now quite secure,

and advances in our understanding of planet formation and evolution can be

achieved by the identification and characterization of an ensemble of debris

disks orbiting a range of central stars with different masses and ages.

Imaging debris disks in starlight scattered by dust grains remains technically

challenging so that only about a dozen systems have thus far been imaged.  A

further advance in this field needs an increased number of imaged debris

disks.  However, the technical challege of such observations, even with the

superb combination of HST and NICMOS, requires the best targets.   Recent HST

imaging investigations of debris disks were sample-limited not limited by the

technology used.  We performed a search for debris disks from a IRAS/Hipparcos

cross correlation which involved an exhaustive background contamination check

to weed out false excess stars.  Out of ~140 identified debris disks, we

selected 22 best targets in terms of dust optical depth and disk angular size.

Our target sample represents the best currently available target set in terms

of both disk brightness and resolvability.  For example, our targets have

higher dust optical depth, in general, than newly identified Spitzer disks.

Also, our targets cover a wider range of central star ages and masses than

previous debris disk surveys. This will help us to investigate planetary

system formation and evolution across the stellar mass spectrum.  The

technical feasibility of this program in two-gyro mode guiding has been proven

with on-orbit calibration and science observations during HST cycles 13, 14,

and 15.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11158

Title:                           HST Imaging of UV emission in Quiescent Early-type Galaxies

PI:                               R. Rich

PI Institution:             University of California - Los Angeles

 

We have constructed a sample of early type galaxies at z~0.1 that have blue

UV-optical colors, yet also show no signs of optical emission, or extended

blue light.  We have cross-correlated the SDSS catalog and the Galaxy

Evolution Explorer Medium Imaging Survey to select a sample of galaxies where

this UV emission is strongest. The origin of the UV rising flux in these

galaxies continues to be debated, and the possibility that some fraction of

these galaxies may be experiencing low levels of star formation cannot be

excluded.   There is also a possibility that low level AGN activity (as

evidenced by a point source) is responsbile  We propose to image the UV

emission using the HST/SBC and to explore the morphology of the UV emission

relative to the optical light.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11159

Title:                           The True Galactic Bulge Luminosity Function

PI:                               R. Rich

PI Institution:             University of California - Los Angeles

 

We propose to obtain second epoch imaging of the deep Galactic bulge field

observed using NICMOS by Zoccali et al. (2000).  The bulge luminosity and mass

function suffered from 30-50% contamination by foreground disk stars, which

was impossible to correct for in the original study.  Revisiting the field

after 9 years, we propose to segregate the foregound disk stars because they

have large transverse velocities, thus revealing the luminosity function of

Galactic bulge low mass stars to near the hydrogen burning limit.  The slope

of the mass function has implications for galaxy formation and for

understanding the nature of microlensing in the Galactic bulge.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11160

Title:                           Escape fraction and stellar populations in a highly magnified Lyman-Break Galaxy

PI:                               Johan Richard

PI Institution:             California Institute of Technology

 

Understanding how star-forming galaxies contribute to cosmic reionization is

one of the frontiers of observational cosmology. A key ingredient in this

issue is measuring the escape fraction of Lyman-continuum photons in high

redshift galaxies (z>3). Gravitationally lensed Lyman-break galaxies (LBGs)

act as important laboratories for studying the resolved physical properties at

sub-kpc scales with high signal-to-noise. Correlating the local escape

fraction with physical parameters derived from stellar population modeling

(such as the star formation rate, age and reddening) will offer new insights

into understanding the physical processes involved with the production of

ionizing photons.  We propose here follow-up observations of the "Cosmic Eye",

a remarkable, highly magnified (x 30), Lyman-break galaxy at z~3.07 using

WFPC2 and NICMOS. Deep ultraviolet WFPC2 imaging will provide a detailed study

of variations in the escape fraction, while WFPC2 and NICMOS/NIC2 imaging will

complement the current broad-band detections to allow a precise modeling of

the spatially-dependent spectral energy distribution. This will allow the

first comprehensive analysis between the escape fraction, the local SED and

the dynamics of a distant galaxy.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11161

Title:                           Revealing the Explosion Geometry of Nearby GRB-SNe

PI:                               Alicia Soderberg

PI Institution:             California Institute of Technology

 

The connection between gamma-ray bursts and Type Ibc supernovae is well-

established in broad terms.  However, our recent identification of an

intermediate class of sub-energetic GRBs, and the overall overlap in Nickel

production between GRB-SNe and ordinary SNe Ibc suggest that the properties

leading to the production of a relativistic engine are yet to be uncovered.  A

fundamental difference between the two classes of explosions may be imprinted

in the overall geometry of the explosion. The relativistic component of GRBs

is known to be highly collimated, but it is unclear if the SN blast is

spherical or mildly collimated as well. Here we propose HST observations of

the late (>30 days) decay tails of two GRB-SNe as an independent measure of

the Nickel mass synthesized in the explosion.  A comparison to the Nickel mass

inferred from the peak brightness of the SNe will provide a direct measure of

the explosion asymmetry, since at late time the explosion is essentially

spherical. These observations will form the core of a multi-wavelength

(optical, X-ray, radio) effort to fully characterize all aspects of the

explosions, from the energy and geometry of the relativistic material (VLA,

Chandra) to the early SN evolution (Keck, Magellan).  The proposed

observations require two slow-response (>30 days) TOOs, ideally suited to the

2-gyro operations of HST.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11162

Title:                           Understanding the Long Term Impacts of Low Magnetic Accretion

PI:                               Paula Szkody

PI Institution:             University of Washington

 

The low accretion rate Polar EF Eri has been in a low state for more than 9

years. Our recent GALEX photometry revealed a source of UV light that is

producing more flux than the white dwarf and which is highly modulated on the

81 min orbital period of the system. We request UV spectra with the SBC on the

ACS to resolve whether limb darkening or cyclotron emission can explain the

observed phenomena and provide insight on the long term heating effects under

low accretion scenarios.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11163

Title:                           Accreting Pulsating White Dwarfs in Cataclysmic Variables

PI:                               Paula Szkody

PI Institution:             University of Washington

 

Recent ground-based observations have increased the number of known pulsating

white dwarfs in close binaries with active mass transfer (cataclysmic

variables) from 5 to 11 systems. Our past Cycles 8 and 11 STIS observations of

the first 2 known, followed by our Cycle 13 SBC observations of the next 3

discovered, revealed the clear presence of the white dwarf and increased

amplitude of the pulsations in the UV compared to the optical. The

temperatures derived from the UV spectra show 4 systems are much hotter than

non-interacting pulsating white dwarfs. A larger sample is needed to sort out

the nature of the instability strip in accreting pulsators i.e. whether

effects of composition and rotation due to accretion result in a well-defined

instability strip as a function of Teff.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11164

Title:                           Molecular Hydrogen Disks Around T Tauri Stars

PI:                               David Weintraub

PI Institution:             Vanderbilt University

 

We propose to measure the properties of planetary system-sized disks around

Sun-like, pre-main sequence stars by imaging the inner parts of these disks

for the first time in gaseous emission from their most dominant constituent,

molecular hydrogen gas. Specifically, we will use the F212N filter and NICMOS

to determine the spatial distribution of ro-vibrational H2 emission from

protoplanetary disks around selected classical and weak-lined T Tauri stars.

The target stars are among those detected by members of this team through high

resolution, ground-based infrared spectroscopy. The spectra reveal H2 emission

at the rest velocities of the stars and at positions spatially coincident with

the stars at the spatial resolution of the spectroscopic data. This imaging

experiment, which is impossible to do using ground-based facilities, is

possible using the NICMOS camera aboard the HST because the point spread

function of this system is extremely stable and can be measured to a very high

accuracy. This experiment is an important test of the interpretation that the

2.122 micron H2 line emission seen toward T Tauri stars is produced at

distances of 10 to 30 AU from the stars, the region in which giant planets are

expected to form around these stars. These observations will contribute toward

developing a better understanding of the process, likelihood, and timescale

for the formation of planets around Sun-like stars.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11165

Title:                           The Radius of the "Super-Neptune" HD 149026b

PI:                               Joshua Winn

PI Institution:             Massachusetts Institute of Technology

 

Current measurements suggest that the transiting exoplanet HD 149026b is a

"super-Neptune," with an enormous heavy-element core. The existence of such a

planet is a major challenge to planet formation theories. We propose to place

the radius measurement on much firmer footing, by obtaining a NICMOS light

curve with 0.4 mmag precision and 13 sec cadence. We will improve the radius

measurement by a factor of 2.3, and more importantly, the result will be more

robust because we will determine the stellar radius directly from the data.

Numerous attempts to do this from the ground have failed.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11166

Title:                           The Mass-dependent Evolution of the Black Hole-Bulge Relations

PI:                               Jong-Hak Woo

PI Institution:             University of California - Santa Barbara

 

In the local universe, the masses of giant black holes  are correlated with

the luminosities, masses and velocity dispersions of their host galaxy bulges.

This indicates a surprisingly close connection between the evolution of

galactic nuclei (on parsec scales) and of stars on kpc scales. A key

observational test of proposed explanations for these correlations is to

measure how they have evolved over cosmic time. Our ACS imaging of 20 Seyfert

1 galaxies at z=0.37 showed them to have smaller bulges (by a factor of 3) for

a given central black hole mass than is found in galaxies in the present-day

universe. However, since all our sample galaxies had black hole masses in the

range 10^8.0--8.5 Msun, we could only measure the OFFSET in black hole mass to

bulge luminosity ratios from the present epoch. By extending this study to

black hole masses another factor of 10 lower, we propose to determine the full

CORRELATION of black hole mass with host galaxy properties at a lookback time

of 4 Gyrs and to test mass-dependency of the evolution. We have selected 14

Seyfert galaxies from SDSS DR5 whose narrow Hbeta emission lines (and

estimated nuclear luminosities) imply that they have black hole masses around

10^7 Msuns. We will soon complete our Keck spectroscopic measures of their

bulge velocity dispersions.  We need a 1-orbit NICMOS image of each galaxy to

separate its nonstellar luminosity from its bulge and disk. This will allow us

to make the first determination of the full black hole/bulge relations at

z=0.37 (e.g. M-L and M-sigma), as well as a test of whether active galaxies

obey the Fundamental Plane relation at that epoch.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11167

Title:                           A Unique High Resolution Window to Two Strongly Lensed Lyman Break Galaxies

PI:                               Sahar Allam

PI Institution:             Fermi National Accelerator Laboratory (FNAL)

 

On rare occasions, the otherwise  very faint Lyman Break Galaxies (LBGs) are

magnified  by gravitational lensing to provide exceptional targets for

detailed spectroscopic and imaging studies. We propose HST WFPC2 and NICMOS

imaging of two strongly lensed Lyman Break Galaxies (LBGs)  that were recently

discovered  by members of  our team.  These two LBGs   -- the "8 O'Clock  Arc"

and the "SDSS  J1206+5142 Arc"  -- are currently the brightest known LBGs,

roughly 3  times brighter than the former  record-holder, MS1512-cB58 (a.k.a.

"cB58"). The z=2.73 "8 O'Clock Arc" extends ~10 arcsec in length and is

magnified by a factor of 12. The  z=2.00 "SDSS J1206+5142 Arc" also extends

~10 arcsec in length and is magnified by a factor of 30.  Due to their

brightness and magnification, these two strongly lensed LBGs offer an

unprecedented opportunity for the very detailed investigation of two

individual galaxies at  high redshift.  We are currently pursuing a vigorous

ground-based campaign to obtain multi-wavelength (UV,  optical, NIR, radio)

observations of  these  two LBGs, but our  campaign  currently lacks a means

of obtaining  high-resolution optical/NIR imaging --  a lack that currently

only HST can address. Our prime objective for this proposal is to obtain high

resolution HST images of these two systems with  two-orbit WFPC2 images in the

BVI bands and two-orbit NICMOS/NIC2 images in the  J and H bands. These data

will allow us to construct detailed lensing models, probe the mass and light

profiles of the lenses and their environments, and constrain the star

formation histories and rest-frame UV/optical spectral energy distributions of

the LBGs.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11168

Title:                           The IMF in the Hidden Galactic Starburst W49A

PI:                               Bernhard Brandl

PI Institution:             Universiteit Leiden

 

W49A is one of the most luminous and prolific massive star formation regions

in the disk of our Milky Way. Given the presence of several very massive OB

clusters as well as an unusually high concentration of many young ultra-

compact HII regions (UCHIIR) -- all embedded in about 1 million solar masses

of molecular gas -- it is arguably the best Galactic template for a luminous

starburst region.   We propose to obtain NICMOS imaging of the central part of

W49A, covering a strip from the central, massive OB cluster to the ring of

UCHIIRs. Our goals are to resolve and characterize the central star cluster

and determine its IMF down to about 1 solar mass. We want to characterize the

distribution of intermediate-mass YSOs, and identify the NIR counterparts to

the UCHIIRs. The combination of the proposed HST/NICMOS data with our recently

obtained Spitzer observations would allow a great step forward in the

understanding of massive star and cluster formation.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11169

Title:                           Collisions in the Kuiper belt

PI:                               Michael Brown

PI Institution:             California Institute of Technology

 

For most of the 15 year history of observations of Kuiper belt objects, it has

been speculated that impacts must have played a major role in shaping the

physical and chemical characteristics of these objects, yet little direct

evidence of the effects of such impacts has been seen. The past 18 months,

however, have seen an explosion of major new discoveries giving some of the

first insights into the influence of this critical process. From a diversity

of observations we have been led to the hypotheses that:     (1) satellite-forming

impacts must have been common in the Kuiper belt; (2) such impacts led to

significant chemical modification; and (3) the outcomes of these impacts are

sufficiently predictable that we can now find and study these impact-derived

systems by the chemical and physical attributes of both the satellites and the

primaries. If our picture is correct, we now have in hand for the first time a

set of incredibly powerful tools to study the frequency and outcome of

collisions in the outer solar system. Here we propose three linked projects

that would answer questions critical to the multiple prongs of our hypothesis.

In these projects we will study the chemical effects of collisions through

spectrophotometric observations of collisionally formed satellites and through

the search for additional satellites around primaries with potential impact

signatures, and we will study the physical effects of impacts through the

examination of tidal evolution in proposed impact systems.  The intensive HST

program that we propose here will allow us to fully test our new hypotheses

and will provide the ability to obtain the first extensive insights into outer

solar system impact processes.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11170

Title:                           UV Imaging of the Martian Corona and the Escape of Hydrogen

PI:                               John Clarke

PI Institution:             Boston University

 

ACS SBC UV imaging observations of Mars are proposed to study the extended

hydrogen corona, with application to the escape of hydrogen and the history of

water on Mars.  These observations will be scheduled when Mars is distant from

the Earth, so that a field of view of +/- 4-5 Mars radii can be obtained to

image the full range of the highly extended martian hydrogen corona through

its H Ly alpha emission.  The observations will also be obtained when the Sun-

Earth-Mars angle is close to 90 degrees, so that any asymmetry along the Mars-

Sun line can be observed.  The observed 2-dimensional brightness distribution

will be related to local density using two existing radiative transfer codes,

and the upward flux and velocity distributions will be determined by

comparison with runs from an exospheric distribution model.  These

observations, combined with simultaneous Ly alpha observations by the SPICAM

instrument on Mars Express from within the atmosphere, will provide the first

tight constraints on the total escape flux and importance of nonthermal

processes on the rate of escape.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11171

Title:                           Confirming Light Echoes from SN 2006X in M100

PI:                               Arlin Crotts

PI Institution:             Columbia University in the City of New York

 

We propose a minimal investment of spacecraft time to discover and confirm a

light echo from Supernova 2006X in M100, the closest Type Ia in many years.

Our spectroscopic and photometric data indicate that this SN sits behind a

large amount of interstellar dust likely to produce a strong echo signal.

This is one of very few cases where we will be able to study the three-

dimensional environment of a SN Ia in full detail, and begin to understand how

environmental effects play into the evolutionary and observational factors

which influence the utility of SN Ia as standard candles for probing

cosmology.  We propose an efficient program to definitively detect (or not) a

light echo of reasonable signal strength, to confirm that it is an echo by

demonstrating apparent superluminal motion if it exists, to map the three-

dimensional geometry of the reflecting interstellar structures, and to detail

the reflectance properties of the dust which can be used to constrain its

grain size and composition distribution.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11172

Title:                           Defining Classes of Long Period Variable Stars in M31

PI:                               Arlin Crotts

PI Institution:             Columbia University in the City of New York

 

We propose a thrifty but information-packed investigation (1440 exposures

total) with NICMOS F205W, F160W and F110W providing crucial information about

Long Period Variables in M31, at a level of detail that has recently allowed

the discovery of new variable star classes in the Magellanic Clouds, a very

different stellar population.  These observations are buttressed by an

extensive map of the same fields with ACS and WFPC2 exposures in F555W and

F814W, and a massive ground-based imaging patrol producing well-sampled light

curves for more than 400,000 variable stars.  Our primary goal is to collect

sufficient NIR data in order to analyze and classify the huge number of long-

period variables in our catalog (see below) through Period-Luminosity (P/L)

diagrams.  We will produce accurate P/L diagrams for both the bulge and a

progression of locations throughout the disk of M31.  These diagrams will be

similar in quality to those currently in the Magellanic Clouds, with their

lower metallicity, radically different star formation history, and larger

spread in distance to the variables.  M31 offers an excellent chance to study

more typical disk populations, in a manner which might be extended to more

distant galaxies where such variables are still visible, probing a much more

evenly spread progenitor age distribution than cepheids (and perhaps useful as

a distance scale alternative or cross-check).  Our data will also provide a

massive and unique color-magnitude dataset, and  allow us to confirm the

microlensing nature of a large sample of candidate lensed sources in M31.  We

expect that this study will produce several important results, among them a

better understanding of P/L and P/L-color relations for pulsating variables

which are essential to the extragalactic distance ladder, will view these

variables at a common distance over a range of metallicities (eliminating the

distance-error vs. metallicity ambiguity between the LMC and SMC), allow

further insight into possible faint-variable mass-loss for higher

metallicities, and in general produce a sample more typical of giant disk

galaxies predominant in many studies.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11173

Title:                           Completing an Accurate Map of M31 Microlensing

PI:                               Arlin Crotts

PI Institution:             Columbia University in the City of New York

 

The halo microlensing masses detected in the MACHO survey (claimed to compose

about 20% of the Galaxy's mass) represent a major enigma in astrophysics, one

that must be effectively cross-examined by an independent test.  We have

completed a large, densely-sampled survey of M31 that can reveal in another

galaxy such a halo microlensing signal if it exists.  In a previous

HST/ACS+WFPC2 program (GO 10273, Cycle 13, 16 orbits) we were able to learn

considerably more about a subsample of these M31 microlensing events.  We were

pleased to find that in most cases we could isolate the source star for each

event, find its baseline flux and colors (essential for ruling out classes of

confusing variable stars), test for misidentification of background

supernovae, and measure the Einstein parameters, which constrain the range of

most likely lens mass.  (These Cycle 13 results are published in The

Astrophysical Journal Letters.)  We propose to finish the job, taking a

similar series of exposures to more than double the sample of well-constrained

microlensing events, which together with the larger ground-based sample for

which we are completing our analyses will provide 20-30 M31 bona fide

microlensing events observed by HST.  This will be done via a series of

targetted PC exposures, meant to maximize the number of candidates studied,

one (or two) at a time.  A sample of this size and quality should be

sufficient to settle the issue of a significant contribution to the halos of

galaxies by stellar-mass lenses.  Furthermore, if there is a surplus of such

microlensing events above what might be expected from stars alone, the higher

quality of information will allow us to more accurately describe the spatial

distribution of these lenses.  We will also complete several unique studies of

M31 stellar populations, both in support of the microlensing measurement and

in their own right.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11174

Title:                           A Spitzer/X-ray candidate cluster at z>2:            NICMOS imaging

PI:                               Emanuele Daddi

PI Institution:             Commissariat a l'Energie Atomique (CEA)

 

We propose deep H-band imaging with NICMOS of a remarkable z>2 cluster of

galaxy candidate. Over a 1000 arcmin^2 field imaged with Spitzer's IRAC and

MIPS we have discovered a compact (<30'' diameter) concentration of extremely

red galaxies with a factor of >40 overdensity over the adjacent field. Among

these galaxies for which we can derive meaningful photometric redshifts, 17

are consistent with zphot=2-2.5, making very likely that the concentrationis

is a real cluster at such high redshift. This is further supported by a 3.5

sigma detection of extended X-Ray emission on Newton-XMM data, by a likely

color-magnitude sequence of red galaxies, and by the presence of a giant

galaxy consistent with a BCG at the cluster redshift. While spectroscopic

confirmation of the cluster might result prohibitive with current facilities,

HST high resolution imaging will allow us to gain crucial information for the

study and scientific exploitation of this hot gas hosting, record high-z

cluster of galaxies. The HST high resolution observations will allow us to

unveil the rest frame optical morphologies of  the galaxies and confirm the

presence of ellipticals in the structure, detect and characterize the color-

magnitude relation, measure their effective radii and construct their Kormendy

relation for the passively evolving subsample, improve the photometric

redshift estimates to confirm the real cluster nature of the structure,

estimate stellar masses and check for possible deviations from the local mass-

size relation, search for mergers and AGNs, and establish a cluster benchmark

for cluster-field comparisons at this highest redshift.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11175

Title:                           UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence

PI:                               Sandra Faber

PI Institution:             University of California - Santa Cruz

 

We have indentified a sample of low-redshift (z = 0.04 - 0.10) galaxies that

are candidates for recent arrival on the red sequence.  They have red optical

colors indicative of old stellar populations, but blue UV-optical colors that

could indicate the presence of a small quantity of continuing or very recent

star formation.  However, their spectra lack the emission lines that

characterize star-forming galaxies.  We propose to use ACS/SBC to obtain high-

resolution imaging of the UV flux in these galaxies, in order to determine the

spatial distribution of the last episode of star formation.  WFPC2 imaging

will provide B, V, and I photometry to measure the main stellar light

distribution of the galaxy for comparison with the UV imaging, as well as to

measure color gradients and the distribution of interstellar dust.  This

detailed morphological information will allow us to investigate the hypothesis

that these galaxies have recently stopped forming stars and to compare the

observed distribution of the last star formation with predictions for several

different mechanisms that may quench star formation in galaxies.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11176

Title:                           Location and the Origin of Short Gamma-Ray Bursts

PI:                               Andrew Fruchter

PI Institution:             Space Telescope Science Institute

 

During the past decade extraordinary progress has been made in determining the

origin of long-duration gamma-ray bursts.   It has been conclusively shown

that these objects derive from the deaths of massive stars.   Nonetheless, the

origin of their observational cousins, short-duration gamma-ray bursts (SGRBs)

remains a mystery.   While SGRBs are widely thought to result from the

inspiral of compact binaries, this is a conjecture.   A number of hosts of

SGRBs have been identified, and have been used by some to argue that SGRBs

derive primarily from an ancient population (~ 5 Gyr); however, it is not

known whether this conclusion more accurately reflects selection biases or

astrophysics.  Here we propose to employ a variant of a technique that we

pioneered and used to great effect in elucidating the origins of long-duration

bursts.   We will examine the degree to which SGRB locations trace the red or

blue light of their hosts, and thus old or young stellar populations.   This

approach will allow us to study the demographics of the SGRB population in a

manner largely free of the distance dependent selection effects which have so

far bedeviled this field, and should give direct insight into the age of the

SGRB progenitor population.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11177

Title:                           The Nature of z=3 Lyman-Alpha Emitters

PI:                               Caryl Gronwall

PI Institution:             The Pennsylvania State University

 

The advent of large mosaic CCD cameras on 4 -- 8 m class telescopes has

recently led to a revolution in our ability to detect primordial galaxies.

Today, large numbers of  strong Ly-alpha emitters (LAEs) are being discovered

between 2.4 < z < 6.  These are important objects:      not only do they sample a

part of the galaxy luminosity function that is inaccessible to the Lyman-break

technique, but they also tend to be younger and less chemically evolved.  In

fact, the LAEs now being found are currently our best candidates for galaxies

in the act of formation.  To investigate the properties of this class of

objects, we have conducted an extremely deep narrow-band (5000 Angstrom; FWHM

= 50 Angstrom) and broad-band (UBVRIzJK) survey of the Extended Chandra Deep

Field South, and have identified a homogeneous sample of strong Ly-alpha

emitters at z = 3.11.  Twenty-seven of these objects are located within the

region surveyed by Great Observatories Origins Deep Survey (GOODS) and have

detailed morphological information available from the rest-frame ultraviolet.

We propose 0.2" resolution narrow-band imaging of 11 of our LAEs using the

F502N filter of WFPC2.  By comparing the Ly-alpha and rest-frame UV continuum

morphologies of these galaxies, we will be able to look for the presence of

outflows, constrain their dust content, and test whether these objects are

truly primordial galaxies.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11178

Title:                           Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries

PI:                               William Grundy

PI Institution:             Lowell Observatory

 

The recent discovery of numerous transneptunian binaries (TNBs) opens a window

into dynamical conditions in the protoplanetary disk where they formed as well

as the history of subsequent events which sculpted the outer Solar System and

emplaced them onto their present day heliocentric orbits.  To date, at least

43 TNBs have been discovered, but only about a dozen have had their mutual

orbits and separate colors determined, frustrating their use to investigate

numerous important scientific questions.  The current shortage of data

especially cripples scientific investigations requiring statistical

comparisons among the ensemble characteristics.  We propose to obtain

sufficient astrometry and photometry of 23 TNBs to compute their mutual orbits

and system masses and to determine separate primary and secondary colors,

roughly tripling the sample for which this information is known, as well as

extending it to include systems of two near-equal size bodies.  To make the

most efficient possible use of HST, we will use a Monte Carlo technique to

optimally schedule our observations.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11179

Title:                           Dynamics of Clumpy Supersonic Flows in Stellar Jets and in the Laboratory

PI:                               Patrick Hartigan

PI Institution:             Rice University

 

We propose to reobserve three stellar jets in order to quantify how rapidly

clumps in these flows accelerate and decelerate, and to compare the results

with ongoing numerical simulations and laboratory experiments. Each jet has

been imaged twice before with HST, and precise proper motions have been

measured for all emitting knots in the jets. Images from the first two epochs

show clear differential motions between adjacent clumps, as well as shear, and

possibly fragmentation. The proposed third epoch will enable us to measure the

first ever accelerations in jets, quantify errors in existing proper motion

measurements, and observe in real time how fluid instabilities develop in

supersonic flows. The new images will make it possible to compare the behavior

of astrophysical flows directly with numerical simulations and with laboratory

experiments of bow shocks and clumpy flows in progress at the Omega laser

facility.

======================================================================

 

Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11180

Title:                           The Morphology of the Post-Red Supergiant IRC+10420's Circumstellar Ejecta

PI:                               Roberta Humphreys

PI Institution:             University of Minnesota - Twin Cities

 

The extremely luminous post-red supergiant and powerful OH/IR source IRC

+10420 is surrounded by a complex circumstellar nebula. Numerous small

condensations, arcs, jet-like rays of knots, and intriguing semi-circular

structures are easily visible in our previous WFPC2 images. We have suggested

that these spatially recognizable features may be evidence for episodic mass

loss events possibly from localized active regions. We now propose to obtain

second epoch WFPC2 images with the Planetary Camera to measure the transverse

motions of these ejecta. Spatially resolved spectra from STIS showed that the

embedded arcs are kinematically distinct from the spherically expanding

diffuse nebulosity. The transverse motions in combination with radial

velocities from the STIS spectra, will let us determine the morphology of IRC

+10420's nebula and the structures embedded in it, its mass loss history, and

provide clues to the mass loss mechanism responsible for the discrete

ejections.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11181

Title:                           SAINTS - Supernova 1987A INTensive Survey

PI:                               Robert Kirshner

PI Institution:             Harvard University

 

SAINTS is a program to observe SN 1987A, the brightest supernova in 383 years,

as it matures into the youngest supernova remnant at age 20.  HST is the

essential tool for spatially-resolved observations of SN1987A's many

components.  A violent encounter is now underway between the fastest-moving

debris and the circumstellar ring: the shock excites "hotspots."  The optical,

infrared and X-ray fluxes are rising rapidly on 6-month time scales:            we have

organized HST, SPITZER, and CHANDRA observations to understand these regions.

In Cycle 16, the separate hotspots may begin to fuse as the shock fully enters

the circumstellar ring.  Photons from these shocks will excite previously

invisible gas outside the ring, revealing the true extent of the mass loss

that preceded the explosion of Sanduleak -69 202. The inner debris of the

explosion, excited by radioactive isotopes from the explosion, is now resolved

and seen to be aspherical, providing direct evidence on the asymmetry of the

explosion.  Questions about SN 1987A remain unanswered. How did the enigmatic

three rings form?  Precisely what happened during the core collapse and

bounce?  Is a black hole or a neutron star left behind?  The rich and deep

data set from SAINTS will help answer these central questions of supernova

science.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11182

Title:                           The Mass of the Milky Way:           Orbits for Leo I and Leo II: Second Epoch Imaging of Leo II

PI:                               Konrad Kuijken

PI Institution:             Universiteit Leiden

 

Constraining the mass of the Galaxy at large radii remains a difficult

problem.  Available data are still rather scarce, and orbits of even a few

objects at large radii can have a large impact.  We propose to obtain proper

motions for the two satellites Leo I and Leo II, which orbit the Galaxy at

about 200 kpc.  Together with the radial velcoities of these glaaxies, which

are well known, the proper motions allow space velocities ot be consructed:

these can remove signifiicant uncertainty in the Galactic mass models, and in

particular settle the vexed question of whether or not Leo I is

gravitationally bound to the Galaxy.  The proper motion of Leo I is addressed

in a companion archival proposal; here we address the WFPC2 imagery of Leo II.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11183

Title:                           Ultraviolet Imaging of Lyman-Alpha-Selected Galaxies at High Redshift

PI:                               Crystal Martin

PI Institution:             University of California - Santa Barbara

 

We propose to carry out deep NICMOS/NIC2 imaging in the rest-frame,

ultraviolet continuum of galaxies discovered in the Magellan Multi-Slit Lyman

Alpha Survey.  This spectroscopic survey identified ultra-faint, redshift 5.7

Lyman-alpha emitters (LAEs) in a 15 nm wide, OH-free band at 819 nm.  Imaging

with HST is the only way to measure their continuum intensity near rest-frame

160 nm.  The ultraviolet photometry will directly measure the rate of star

formation in common objects; and, when combined with groundbased Lyman-alpha

luminosities, provide a reliable cross-calibration of Lyman-alpha attenuation

and emission equivalent width.  Direct measurement of the size of the star-

forming regions, unresolved in the groundbased data, will extend measurements

of the intensity of star formation to common objects in the high-redshift

universe.  Gaseous outflows from these galaxies are thought to be the source

of their asymmetric line profiles, and area-averaged star formation rates are

needed to calibrate feedback recipes, as well as eventually extend the

Schmidt-Kennicutt law to high-redshift.  The three targets proposed in

Cycle~16 lie in fields covered by major galaxy surveys, are not as bright as

the unusually luminous sources identified by such surveys at high-redshift,

and present an opportunity to study properties of more common galaxies at

high-redshift.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11184

Title:                           Imaging the Shock Precursor in Tycho's SNR

PI:                               John Raymond

PI Institution:             Smithsonian Institution Astrophysical Observatory

 

Cosmic ray acceleration in supernova remant shocks requires shock precursors

where particles are trapped by plasma turbulence.  The precursors also heat

and compress the upstream gas, producing H alpha emission and affecting line

profiles.  We propose to image the brightest non-radiative shock in Tycho's

SNR to measure the brightness and width of the precursor.  These measurements

will constrain 2 key parameters in cosmic ray acceleration models, and they

will improve the accuracy of shock speed and electron-ion equilibration

derived from H alpha profiles.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11185

Title:                           Search for H-poor/He-rich Inclusions and a Solution to the Abundance, Temperature Problems

PI:                               Robert Rubin

PI Institution:             NASA Ames Research Center

 

Our recent abundance survey of a large sample of Galactic planetary nebulae

(PNe) has led to the discovery of a group  of super-metal-rich nebulae whose

spectra are characterized by prominent optical recombination lines (ORLs) from

C, N, O, & Ne ions and a large Balmer discontinuity jump. The heavy element

abundances derived from ORLs for several PNe are more than an order of

magnitude higher than those derived from the traditional method based on

collisionally excited lines (CELs), while the Balmer jump yields electron

temperatures (Te) significantly lower than values derived from the [O III]

5007/4363 CEL line ratio.   A proposition that aspires to explain both the

nebular abundance and Te problems is one  according to which these nebulae

contain (at least) two distinct emission regions - one of "normal" Te (~ 10000

K) and chemical composition (~solar) and another of very low Te that is H-

deficient, thus having high helium and metal abundances relative to hydrogen.

The latter component emits strong He and heavy element ORLs but essentially no

CELs. The consistent picture that emerges from fitting a 2-component

photoionization model to the spectroscopic data is that the H-poor component

is in high-density inclusions, which provide only a minor fraction of the

total nebular mass. We propose to directly detect these inclusions in the

planetary nebula M 1-42 using WFPC2 (PC) to make a high spatial resolution

image in the He I  5876 A  ORL and ratio it to Halpha. With NICMOS (NIC1), we

plan to observe the He I 10830 A line, which is  substantially collisionally

excited, along with Palpha 18760 A. The ratio image of He I 10830 to Palpha is

expected to be  less likely to show the inclusions, thus serving as an

important control to the optical imaging. M 1-42 is one of the most extreme

cases of the abundance and Te problem; it is reasonably bright and compact.

This program has the potential to resolve a serious challenge to our current

understanding of nebular astrophysics.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11186

Title:                           Investigation of the spatial and temporal structure of Europa's atmospheric emissisons

PI:                               Joachim Saur

PI Institution:             Universitat zu Koeln

 

We propose to explore the spatial structure and temporal variability of

Europa's O2 atmosphere with ACS/SBC. Previous HST images display non-uniform

UV emission from Europa's atmosphere, which maximizes within the disk of

Europa on its anti-Jovian northern quadrant. These images were taken at

western elongation and are  not conclusive, but bring up the exciting question

whether the non-uniform emission is due to a locally  enhanced neutral

atmosphere. A locally inhomogeneous atmosphere would imply locally modified

surface  properties. This might provide clues on inhomogeneities of the

underlying ice structure and thus properties of a  potential subsurface ocean.

Since the inhomogeneous emission comes from within the disk of Europa, we

propose to study Europa at eastern and western elongation to decide if the

locally enhanced emission is truly an  atmospheric effect. We propose to take

for each elongation five contiguous observations within one rotation  period

of Jupiter to discriminate between a competing effect that produces

inhomogeneous emission patterns,  i.e., the electrodynamic interaction with

Jupiter's magnetosphere. We will use ACS/SBC with PR130L prism to  completely

separate the two prominent FUV oxygen lines OI 1304 A and OI 1356 A emitted

from Europa's  atmosphere.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11187

Title:                           A Deep Search for Martian Dust Rings

PI:                               Mark Showalter

PI Institution:             SETI Institute

 

It has been long suspected that Mars is encircled by two faint rings of dust,

one originating from each of its moons Phobos and Deimos. Similar dust rings

are associated with many of the small, inner moons orbiting Jupiter, Saturn,

Uranus and Neptune. On December 31, 2007, Earth will pass through Mars'

equatorial plane just a week after its December 24 opposition, providing an

exceedingly rare opportunity to image the rings under nearly ideal viewing

geometry. The next equivalent viewing opportunity occurs in 2022. Using the

Wide Fields of WFPC2 and a highly optimized observing plan, we expect to be

able to detect rings with edge-on reflectivities of ~ 10^-8, which is at or

below the level where most dynamicists expect rings to be visible. This is a

factor of 10-30 more sensitive than the detection limit we achieved during a

slightly inferior viewing opportunity in 2001. The rings have been predicted

to show some interesting dynamical properties, including large asymmetries and

inclinations. A positive detection will test these predictions, serving as an

effective test of dynamical models developed to account for the properties of

other faint planetary rings as well. With such a stringent limit, even a

negative result will be of considerable interest, challenging dynamicists to

explain the remarkably low density of dust within the Martian system.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11188

Title:                           First Resolved Imaging of Escaping Lyman Continuum

PI:                               Brian Siana

PI Institution:             Jet Propulsion Laboratory

 

The emission from star-forming galaxies appears to be responsible for

reionization of the universe at z>6.  However, the models that attempt to

describe the detailed impact of high-redshift galaxies on the surrounding

inter-galactic medium (IGM) are strongly dependent upon several uncertain

parameters.  Perhaps the most uncertain is the fraction of HI-ionizing photons

produced by young stars which escape into the IGM.  Most attempts to measure

this "escape fraction" (f_esc) have produced null results.  Recently, a small

subset of z~3 Lyman Break Galaxies (LBGs) has been found exhibiting large

escape fractions.  It remains unclear however, what differentiates them from

other LBGs.  Several models attempt to explain how such a large fraction of

ionizing continuum can escape through the HI and dust in the ISM (eg.

"chimneys" created by SNe winds, globular cluster formation, etc.), each

producing unique signatures which can be observed with resolved imaging of the

escaping Lyman continuum.  We propose a deep, high resolution WFPC2 image of

the ionizing continuum (F336W) and the rest-frame 1500 Angstrom continuum

(F606W) of five of the six known LBGs with large escape fractions.  These LBGs

all fit within a single WFPC2 pointing, yielding high observing efficiency.

Additionally, they all have z~3.1 or higher, the optimal redshift range for

probing the Lyman Continuum region with available WFPC2 filters.  These

factors make our proposed sample especially suitable for follow-up.  With

these data we will discern the mechanisms responsible for producing large

escape fractions, and therefore gain insight into the process of reionization.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11189

Title:                           Probing the early universe with GRBs

PI:                               Nial Tanvir

PI Institution:             University of Leicester

 

Cosmology is beginning to constrain the nature of the earliest stars and

galaxies to form in the Universe, but direct observation of galaxies at z>6

remains highly challenging due to their scarcity, intrinsically small size,

and high luminosity distance.  GRB afterglows, thanks to their extreme

luminosities, offer the possibility of circumventing these normal constraints

by providing redshifts and spectral information which couldn't be obtained

through direct observation of the host galaxies themselves.  In addition, the

association of GRBs with massive stars means that they are an indicator of

star formation, and that their hosts are likely responsible for a large

proportion of the ionizing radiation during that era.  Our collaboration is

conducting a campaign to rapidly identify and study candidate very high

redshift bursts, bringing to bear a network of 2, 4 and 8m telescopes with

near-IR instrumentation.  Swift has proven capable of detecting faint, distant

GRBs, and reporting accurate positions for many bursts in near real-time.

Here we propose to continue our HST program of targetting GRBs at z~6 and

above.  HST is crucial to this endeavour, allowing us (a) to characterise the

basic properties, such as luminosity and colour, and in some cases

morphologies, of the hosts, which is essential to understanding these

primordial galaxies and their relationship to other galaxy populations; and

(b) to monitor the late time afterglows and hence compare them to lower-z

bursts and test the use of GRBs as standard candles.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11190

Title:                           Probing Uranus' Vertical Aerosol Structure at Equinox

PI:                               Laurence Trafton

PI Institution:             University of Texas at Austin

 

After a decade of quiescence following the Voyager flybys, Uranus' atmosphere

has been exhibiting increasing activity approaching equinox that suggests a

short timescale, dynamical, response in addition to a long timescale,

radiative, response to the seasonal change of hemispheric heating.  We propose

to investigate this dichotomy by measuring Uranus' vertical aerosol structure

over the entire surface, including both poles, at equinox when the forcing

insolation is hemispherically symmetric, requiring that the sub-Earth latitude

be less than a degree. Only at equinox (every 42 years) can the entire surface

of the planet be viewed (over a full rotation) and mapped with the same

viewing geometry. We will probe the morphology of the vertical haze structure

using NICMOS narrow band filters beyond 1 micron to isolate different altitude

regimes between the stratosphere and cloud deck and investigate its change

since Cycle 7. We will use two complementary approaches: First, imaging will

be done using medium- and narrow-band filters first to locate the dynamically-

produced discrete cloud features, then to probe their vertical structure and

morphology. The methane absorption bands are stronger in the proposed near-IR

(1 to 2.5 microns) than at shorter wavelengths, and the strong H2 pressure-

induced absorption from 2.1-2.4 microns contributes to the peak opacity. This

enhances the visibility of  transient, spatially isolated features and allows

their structure to be probed to higher altitudes; namely, to the upper

troposphere where they would be evidence of convective overshoot, a dynamical

manifestation that would support strong seasonally-induced static instability.

In addition to probing the structure with filter photometry, we will measure

longitudinal limb profiles to probe the vertical background haze distribution

vs latitude. HST/NICMOS is required because it avoids telluric water

absorption and OH+O2 emission, and has a stable, well-characterized PSF,

essential for limb studies and extracting the vertical structure of fine

features crossing the disk. The proposed observations would complement the

ground-based Uranus equinox campaign.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11191

Title:                           NICMOS Imaging of a z>4 High-Redshift Ultraluminous Submillimeter Source

PI:                               Wei-Hao Wang

PI Institution:             Associated Universities, Inc.

 

We propose 16 orbits of deep NICMOS 1.6 um imaging of GOODS850-5, a unique z>4

candidate SCUBA source that is bright in the submillimeter (submm) but

extremely faint at all other wavelengths.  GOODS850-5 is a 11 mJy 850 um

source discovered in our GOODS-N SCUBA survey.  It does not have a radio

counterpart and its accurate location was recently determined with the SMA

interferometer.  It is not detected by the GOODS-N HST ACS imaging and is just

above the detection limit of the ultradeep Spitzer imaging at 3.6-24 um.  Its

faint radio flux and its Spitzer color suggest a redshift of z>4, and

potentially even z>6.  It has an incredible star formation rate of ~1000 solar

mass per year, and it can quickly grow into a >10^11 solar mass massive

galaxy.  Radio faint submm sources like GOODS850-5 may be a new population of

high-redshift massive galaxies that are not picked up by any of the previous

optical, near-IR, and radio surveys, and therefore it is crucial to obtain the

redshift of GOODS850-5.  However, because of its extreme optical faintness,

the only way to constrain its redshift is photometric redshift with the

existing Spitzer photometry and the proposed NICMOS 1.6 um photometry.  NICMOS

is the only instrument that can provide information about its redshift and

morphology among all space-based and ground-based instruments at all

wavelengths.  The proposed observation will provide unique insight on galaxy

evolution and mass assembly at high redshift.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11192

Title:                           NICMOS Confirmation of Candidates of the Most Luminous Galaxies at z > 7

PI:                               Hao-Jing Yan

PI Institution:             Observatories of the Carnegie Institution of Washington

 

While the deepest pencil-beam near-IR survey suggested that the Universe was

too young to build up many luminous galaxies by z ~ 7--8 (Bouwens &

Illingworth 2006), there is also evidenc indicating the contrary. It is now

known that some galaxies with stellar masses of M>1e10 Msun were already in

place by z ~ 6--7, which strongly suggests that their progenitors should be

significantly more luminous, and hence detectable in deep, wide-field near-IR

surveys (Yan et al. 2006). As galaxies at such a high redshift should manifest

themselves as "dropouts" from the optical,  we have carried out a very wide-

field, deep near-IR survey in the GOODS fields to search for z-band dropouts

as candidates of galaxies at z > 7. In total, six promising candidates have

been found in ~ 300 sq. arcmin to J_AB ~ 24.5 mag (corresponding to  restframe

M(UV) < -22.5 mag at z ~ 7).  By constrast, the galaxy luminosity function

(LF) suggested in BI06 would predict at most 3--5 galaxies over the entire 2-

pi sky at this brightness level.  Here we propose to observe these candidates

with NIC3 in F110W and F160W to further investigate their nature. If any of

these candidates are indeed at z > 7,  the result will lead to a completely

new picture of star formation in the early universe. If none of our candidates

are consistent with being at z > 7, then the depth and area of our near-IR

survey (from which the candidates are drawn) will let us set a very stringent

upper limit on the bright end of the galaxy LF at those redshift.  As a

result, our program will still be able to provide new clues about the

processes of early galaxy formation, such as their dust contents and their

merging time scale (Yan et al. 2006).

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11193

Title:                           A comprehensive study of the low-mass stellar population in the Galactic starburst region NGC 3603

PI:                               Wolfgang Brandner

PI Institution:             University of California - Los Angeles

 

NGC 3603, located in the Carina spiral arm, is one of the most luminous giant

HII regions in the Milky Way, and as such it is often referred to as a prime

template for extragalactic starbursts. While previous studies were focussing

on the high and intermediate mass stellar content of the central starburst

cluster, which powers the HII region, the effects of the starburst environment

with its large number of ionizing O stars on the emerging low-mass population

are unknown. As the most nearby, most easily accessible starburst, NGC 3603

provides the best testbed to study the long-lived, low-mass stars originating

from a starburst environment. Taking advantage of the large field of view and

high sensitivity of WFPC2, we want to survey the stellar population in an area

of 10pc x 10pc (6' x 6') down to a mass limit of 0.2 to 0.5 Mo.  This will

enable us to derive the total cluster mass, look for spatial variations in the

initial mass function, determine the age of the dispersed low-mass population

in the HII region and search for evidence of sequential star formation.

Ultimately, we aim at reconstructing the low-mass stellar initial mass

function of the starburst epoch in NGC 3603, which in turn will advance our

understanding of extragalactic starburst phenomena and the emerging low-mass

stars as observed in ancient populations. The observations of NGC 3603 are

part of our larger effort to study intense star-forming regions in the Milky

Way, LMC and SMC.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11194

Title:                           Beyond the Bullet:   Direct Detection of Dark Matter in Merging Galaxy Clusters

PI:                               Douglas Clowe

PI Institution:             Ohio University

 

Our comparison of the distribution of baryons (stars and gas) and mass (from

weak lensing) in the "Bullet" Cluster has recently yielded concrete evidence

for dark matter independent of basic assumptions regarding the nature of the

gravitational force. The one incomplete aspect of the argument relates to

potential, although highly unlikely, coincidences (special alignments along

the line of sight, and/or fortuitious canceling in non-standard gravitational

models) that can always be invoked against results derived from the study of

one object.  Therefore, we proprose to complete this line of investitgation by

increasing the size of our sample with obsevations of two additional clusters.

Here we propose to obtain HST WFPC2 imaging mosaics around the cores of both

clusters to detect at high significance if the weak gravitational lensing mass

peaks are routinely displaced from the X-ray plasma clouds and aligned with

the galaxy concentrations in interacting clusters.  With a relatively modest

allocation of time, we seek to complete a significant step toward the eventual

resolution of the dark matter question.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11195

Title:                           Morphologies of the Most Extreme High-Redshift Mid-IR- luminous Galaxies II:   The `Bump' Sources

PI:                               Arjun Dey

PI Institution:             National Optical Astronomy Observatories, AURA

 

The formative phase of some of the most massive galaxies may be extremely

luminous, characterized by intense star- and AGN-formation.  Till now, few

such galaxies have been unambiguously identified at high redshift, and thus

far we have been restricted to studying the low-redshift ultraluminous

infrared galaxies as possible analogs. We have recently discovered a sample of

objects which may indeed represent this early phase in galaxy formation, and

are undertaking an extensive multiwavelength study of this population. These

objects are optically extremely faint (R>26) but nevertheless bright at mid-

infrared wavelengths (F[24um] > 0.5 mJy). Mid-infrared spectroscopy with

Spitzer/IRS reveals that they have redshifts z~2, implying luminosities  ~1E13

Lsun.  Their mid-IR SEDs fall into two broad, perhaps overlapping, categories.

Sources with brighter F[24um] exhibit power-law SEDs and SiO absorption

features in their mid-IR spectra characteristic of AGN, whereas those with

fainter F[24um] show a "bump" characteristic of the redshifted 1.6um peak from

a stellar population, and PAH emission characteristic of starformation.  We

have begun obtaining HST images of the brighter sources in Cycle 15 to obtain

identifications and determine kpc-scale morphologies for these galaxies. Here,

we aim to target the second class (the "bump" sources) with the goal of

determining if these constitute morphologically different objects, or simply a

"low-AGN" state of the brighter class.  The proposed observations will help us

determine whether these objects are merging systems, massive obscured

starbursts (with obscuration on kpc scales

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11196

Title:                           An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe

PI:                               Aaron Evans

PI Institution:             State University of New York at Stony Brook

 

At luminosities above 10^11.4 L_sun, the space density of far-infrared

selected galaxies exceeds that of optically selected galaxies. These Luminous

Infrared Galaxies (LIRGs) are primarily interacting or merging disk galaxies

undergoing starbursts and creating/fueling central AGN. We propose far

(ACS/SBC/F140LP) and  near (WFPC2/PC/F218W) UV imaging of a sample of 27

galaxies drawn from the complete IRAS Revised Bright Galaxy Sample (RBGS)

LIRGs sample and known, from our Cycle 14 B and I-band ACS imaging

observations, to  have significant numbers of  bright (23 < B < 21 mag) star

clusters in the central 30 arcsec.  The HST UV data will be combined with

previously obtained HST, Spitzer, and GALEX images to (i) calculate the ages

of the clusters as function of merger stage, (ii) measure the amount of UV

light in massive star clusters relative to diffuse regions of star formation,

(iii) assess the feasibility of using the UV slope to predict the far-IR

luminosity (and thus the star formation rate) both among and within IR-

luminous galaxies, and (iv) provide a much needed catalog of rest-frame UV

morphologies for comparison with rest-frame UV images of high-z LIRGs and

Lyman Break Galaxies. These observations will achieve the resolution required

to perform both detailed photometry of compact structures and spatial

correlations between UV and redder wavelengths for a physical interpretation

our IRX-Beta results. The HST UV data, combined with the HST ACS, Spitzer,

Chandra, and GALEX observations of this sample, will result in the most

comprehensive study of luminous starburst galaxies to date.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11197

Title:                           Sweeping Away the Dust:  Reliable Dark Energy with an Infrared Hubble Diagram

PI:                               Peter Garnavich

PI Institution:             University of Notre Dame

 

We propose building a high-z Hubble Diagram using type Ia supernovae observed

in the infrared rest-frame J-band. The infrared has a number of exceptional

properties.  The effect of dust extinction is minimal, reducing a major

systematic that may be biasing dark energy measurements.  Also, recent work

indicates that type Ia supernovae are true standard candles in the infrared

meaning that our Hubble diagram will be resistant to possible evolution in the

Phillip's relation over cosmic time. High signal-to-noise measurements of 16

type Ia events at z~0.4 will be compared with an independent optical Hubble

diagram from the ESSENCE project to test for a shift in the derived dark

energy equation of state due to a systematic bias.  In Cycle 15 we obtained

NICMOS photometry of 8 ESSENCE supernovae and are awaiting template

observations to place them on the IR Hubble diagram. Here we request another 8

supernovae be studied in the final season of the ESSENCE search.  Because of

the bright sky background, H-band photometry of z~0.4 supernovae is not

feasible from the ground. Only the superb image quality and dark infrared sky

seen by HST makes this test possible. This experiment may also lead to a

better, more reliable way of mapping the expansion history of the universe

with the Joint Dark Energy Mission.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11198

Title:                           Pure Parallel Imaging in the NDWFS Bootes Field

PI:                               Anthony Gonzalez

PI Institution:             University of Florida

 

The NOAO Deep-Wide Field Survey (NDWFS) Bootes field is the target of one of

the most extensive multiwavelength campaigns in astronomy.  In addition to

ground-based optical and near-infrared imaging, deep radio mapping, and

extensive spectroscopy, this entire region has been imaged by the Chandra,

Spitzer (IRAC and MIPS), and GALEX missions.  Robust photometric redshifts

(calibrated using over 20,000 spectroscopic redshifts) exist for all sources

brighter than R=24.5 or than 13 uJy at 4.5 microns.  To enhance the value of

this data set, we propose pure parallel observations for all approved Cycle 16

programs in this region that lack coordinated parallel observations.  The

primary aim of this program will be to provide a database useful for the broad

range of science programs underway in this region.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11199

Title:                           A Hard Look at Stellar Disks at the Epoch of Planet Formation

PI:                               Lee Hartmann

PI Institution:             University of Michigan

 

We propose to use HST/ACS/SBC and Chandra/ACIS-S3 to observe the high energy

fluxes of 4 stars surrounded by disks in the newly discovered aggregate 25

Ori, the most populous 10 Myr group known within 500 pc. Our observations will

cover the 1-25A and 1250-2000A bandpasses, and will complement our optical and

Spitzer data for these objects, to provide essential input to physically-

consistent models of disk structure and chemistry in the age range around 10

Myr, thought to be a critical period in the planet-forming process.  We will

be able to determine the Ne/O ratio and determine if the anomalous metal

abundances observed in X-ray spectra of young stars are an evolutionary or an

environmental effect.  Our proposed observations will double the number of 10

Myr old accreting stars with known high energy radiation fields, and will be

the first FUV observations of low mass accreting stars in an OB association.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11200

Title:                           An Ultraluminous EUV Source?

PI:                               Philip Kaaret

PI Institution:             University of Iowa

 

Ultraluminous X-ray sources (ULXs) are bright, irregularly variable, non-

nuclear, X-ray sources with apparent luminosities exceeding the Eddington

limit for stellar-mass black holes.  There is great interest in ULXs because

they may represent a new class of black holes with masses intermediate between

stellar-mass and supermassive black holes.  Recently, it has been found that

X-ray emission from the nebula MF 16 in the galaxy NGC 6946, previously

thought to be an usually luminous supernova remnant, actually arises from an

accreting compact object.  Optical spectroscopy of nebula shows that it is

powered via photoionization by an extreme ultraviolet (EUV) source with a

luminosity exceeding that measured from the X-ray source.  If correct this

would be the first ultraluminous UV source and may be a 10,000 solar mass

black hole.  We propose an FUV observation with the ACS/SBC to determine if a

highly luminous EUV source is indeed, present within MF 16.

======================================================================

 

Proposal Category: SNAP

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11201

Title:                           Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images

PI:                               Nitya Kallivayalil

PI Institution:             Harvard University

 

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the

Magellanic Clouds centered on background quasars. We used these data to

determine the proper motions of the LMC and SMC to better than 5% and 15%

respectively. These are by far the best determinations of the proper motions

of these two galaxies. The results have a number of unexpected implications

for the Milky Way-LMC-SMC system. The implied three-dimensional velocities are

larger than previously believed, and are not much less than the escape

velocity in a standard 10^12 solar mass Milky Way dark halo. Orbit

calculations suggest the Clouds may not be bound to the Milky Way or may just

be on their first passage, both of which would be unexpected in view of

traditional interpretations of the Magellanic Stream. Alternatively, the Milky

Way dark halo may be a factor of two more massive than previously believed,

which would be suprising in view of other observational constraints. Also, the

relative velocity between the LMC and SMC is larger than expected, leaving

open the possibility that the Clouds may not be bound to each other. To

further verify and refine our results we now request an epoch of WFPC2/PC data

for the fields centered on 40 quasars that have at least one epoch of ACS

imaging. We request execution in snapshot mode, as in our previous programs,

to ensure the most efficient use of HST resources. A third epoch of data of

these fields will provide crucial information to verify that there are no

residual systematic effects in our previous measurements. More importantly, it

will increase the time baseline from 2 to 5 yrs and will increase the number

of fields with at least two epochs of data. This will reduce our uncertainties

correspondingly, so that we can better address whether the Clouds are indeed

bound to each other and to the Milky Way. It will also allow us to constrain

the internal motions of various populations within the Clouds, and will allow

us to determine a distance to the LMC using rotational parallax.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11202

Title:                           The Structure of Early-type Galaxies:      0.1-100 Effective Radii

PI:                               Leon Koopmans

PI Institution:             Kapteyn Astronomical Institute

 

The structure, formation and evolution of early-type galaxies is still largely

an open problem in cosmology:   how does the Universe evolve from large linear

scales dominated by dark matter to the highly non-linear scales of galaxies,

where baryons and dark matter both play important, interacting, roles? To

understand the complex physical processes involved in their formation

scenario, and why they have the tight scaling relations that we observe today

(e.g. the Fundamental Plane), it is critically important not only to

undertstand their stellar structure, but also their dark-matter distribution

from the smallest to the largest scales.  Over the last three years the SLACS

collaboration has developed a toolbox to tackle these issues in a unique and

encompassing way by combining new non-parametric strong lensing techniques,

stellar dynamics, and most recently weak gravitational lensing, with high-

quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of

early-type lens systems. This allows us to break degeneracies that are

inherent to each of these techniques seperately and probe the mass structure

of early-type galaxies from 0.1 to 100 effective radii. The large dynamic

range to which lensing is sentive allows us both to probe the clumpy

substructure of these galaxies, as well as their low-density outer haloes.

These methods have convincingly been demonstrated, by our team, using smaller

pilot-samples of SLACS lens systems with HST data.  In this proposal, we

request observing time with WFPC2 and NICMOS to observe 53 strong lens systems

from SLACS, to obtain complete multi-color imaging for each system. This would

bring the total number of SLACS lens systems to 87 with completed HST imaging

and effectively doubles the known number of galaxy-scale strong lenses. The

deep HST images enable us to fully exploit our new techniques, beat down low-

number statistics, and probe the structure and evolution of early-type

galaxies, not only with a uniform data-set an order of magnitude larger than

what is available now, but also with a fully coherent and self-consistent

methodological approach

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11203

Title:                           A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus

PI:                               Kevin Luhman

PI Institution:             The Pennsylvania State University

 

During a 1-orbit program in Cycle 14, we used WFPC2 to obtain the first direct

image of a circumstellar disk around a brown dwarf. These data have provided

fundamental new constraints on the formation process of brown dwarfs and the

properties of their disks. To search for additional direct detections of disks

around brown dwarfs and to search for planetary-mass companions to these

objects, we propose a WFPC2 survey of 32 brown dwarfs in the Taurus star-

forming region.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11204

Title:                           Imaging Circumstellar Disks and Envelopes around Proto- Brown Dwarfs

PI:                               Kevin Luhman

PI Institution:             The Pennsylvania State University

 

Using the Spitzer Space Telescope, we have discovered two young brown dwarfs

with Class I spectral energy distributions (i.e., proto-brown dwarfs). We

propose to perform broad-band NICMOS imaging of these Class I brown dwarfs to

spatially resolve their circumstellar disks and envelopes. If successful,

these data would comprise the first measurements of this kind for brown dwarfs

and would provide fundamental constraints on models for the formation of brown

dwarfs.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11205

Title:                           The Effects of Multiplicity on the Evolution of Young Stellar Objects:            A NICMOS Imaging Study

PI:                               James Muzerolle

PI Institution:             University of Arizona

 

We propose to use NICMOS to investigate the multiplicity of young stellar

objects (YSOs) in the Orion B molecular cloud.  Previous observations with the

Spitzer Space Telescope have revealed a remarkable star forming filament near

the NGC 2068 reflection nebula.  The population of YSOs associated with the

filament exhibit a surprisingly wide range of circumstellar evolutionary

states, from deeply embedded protostars to T Tauri accretion disks.  Many of

the circumstellar disks themselves show evidence for significant dust

evolution, including grain growth and settling and cleared inner holes,

apparently in spite of the very young age of these stars.  We will estimate

the binary fraction of a representative sample of objects in these various

stages of evolution in order to test whether companions may play a significant

role in that evolution.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11206

Title:                           At the cradle of the Milky Way:      Formation of the most massive field disk galaxies at z>1

PI:                               Kai Noeske

PI Institution:             University of California - Santa Cruz

 

We propose to obtain 2 orbit WFPC2 F814W images of a sample of the 15 most

massive galaxies found at $1 < z < 1.3$. These were culled from over 20,000

Keck spectra collected as part of DEEP and are unique among high redshift

massive galaxy samples in being kinematically selected.   Through a recent HST

NICMOS-2 imaging program (GO-10532), we have confirmed that these  galaxies

have regular stellar disks, and their emission line kinematics are not due to

gradients from merging components. These potentially very young galaxies are

likely precursors to massive local disks, assuming no further merging.   The

proposed WFPC2 and existing NIC-2 data provide colors, stellar masses, and

ages of bulge and disk subcomponents,  to assess whether old stellar bulges

and disks are in place at that time or still being built, and constrain their

formation epochs. Finally,  this sample will yield the first statistically

significant results on the $z > 1$ evolution of the size-velocity-luminosity

scaling relations, for massive galaxies at different wavelengths, and

constrain whether this evolution reflects stellar mass growth, or passive

evolution, of either bulge or disk components.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11207

Title:                           Star Formation in the Perseus Cluster Cooling Flow

PI:                               Robert O'Connell

PI Institution:             The University of Virginia

 

We propose to obtain high resolution, UV/optical imaging of the "accretion

populations" in the massive cooling flow of the Perseus cluster of galaxies.

New GALEX observations show that the dominant galaxy in this nearby cluster,

NGC 1275, has an extended network of UV-bright populations apparently formed

recently from the intracluster gas.  Cluster cooling flows are the most

prominent of the environments where we can readily observe the cycle of gas

accretion, star formation, and feedback from active nuclei that is thought to

play a central role in the formation and evolution of galaxies.  Because they

can be readily age-dated, the accretion populations help to trace the sequence

of exchange of material between galaxies and the intracluster medium.  The

ACS/SBC and WFPC2/PC cameras offer the highest spatial resolution and best

panchromatic performance available to map the spatial and age distribution of

the accretion populations and their relationship to radio-emitting plasma and

the hot intracluster gas.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11208

Title:                           The co-evolution of spheroids and black holes in the last six billion years

PI:                               Tommaso Treu

PI Institution:             University of California - Santa Barbara

 

The masses of giant black holes are correlated with the luminosities, masses,

and velocity dispersions of the bulges of their host galaxies. This empirical

correlation of phenomena on widely different scales (from pcs to kpcs)

suggests that the formation and evolution of galaxies and central black holes

are closely linked. In Cycle 13, we have started a campaign to map directly

the co-evolution of spheroids and black-holes by measuring in observationally

favorable redshift windows the empirical correlations connecting their

properties. By focusing on Seyfert 1s, where the nucleus and the stars

contribute comparable fractions of total light, black hole mass and bulge

dispersion are obtained from Keck spectroscopy. HST is required for accurate

measurement of the non stellar AGN continuum, the morphology of the galaxy,

and the structural parameters of the bulge. The results at z=0.36 indicate a

surprisingly fast evolution of bulges in the past 4 Gyrs (significant at the

95%CL), in the sense that bulges were significantly smaller for a given black

hole mass. Also, the large fraction of mergers and disturbed galaxies (4+2 out

of 20) identifies gas-rich mergers as the mechanisms responsible for bulge-

growth. Going to higher redshift -- where evolutionary trends should be

stronger --  is needed to confirm these tantalizing results. We propose

therefore to push our investigation to the next suitable redshift window

z=0.57 (lookback-time 6 Gyrs). Fifteen objects are the minimum number required

to map the evolution of the empirical correlations between bulge properties

and black-hole mass, and to achieve a conclusive detection of evolution

(>99%CL).

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11209

Title:                           Determining the Structural Parameters of the First Globular Cluster Found to Host an Black-Hole X-ray Binary

PI:                               Stephen Zepf

PI Institution:             Michigan State University

 

We recently published the discovery of the first black hole X-ray binary in a

globular cluster. This object is located in a bright globular cluster around

the Virgo elliptical NGC 4472. Here we propose to obtain HST PC images of this

black-hole hosting globular cluster and a sample of other NGC 4472 globulars.

We will use these data to determine the structural parameters of both the

globular cluster known to have a black hole and a control sample of other NGC

4472 clusters. This will test recent theoretical predictions how black holes

affect the structural parameters of globular clusters, and more generally will

allow for the first time constraints on any relationship between the presence

of a black hole and the surface brightness profiles of globular clusters. The

deep WFPC2 images outside of the galaxy's central regions will also be

invaluable for studying how the sizes and luminosity function of globular

clusters depend on distance from the center of the galaxy, and thus address

questions about the origin of the size differences between metal-rich and

metal-poor clusters and the shape of the globular cluster luminosity function.

In addition, parallel NIC3 images will allow the optical to near-infrared

colors of NGC 4472 globular cluster to be determined over a wide range of

galactocentric radii.

======================================================================

 

Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11210

Title:                           The Architecture of Exoplanetary Systems

PI:                               George Benedict

PI Institution:             University of Texas at Austin

 

Are all planetary systems coplanar? Concordance cosmogony makes that

prediction. It is, however, a prediction of extrasolar planetary system

architecture as yet untested by direct observation for main sequence stars

other than the Sun.  To provide such a test, we propose to carry out FGS

astrometric studies on four stars hosting  seven companions. Our understanding

of the planet formation process will grow as we match not only system

architecture, but formed planet mass and true distance from the primary with

host star characteristics for a wide variety of host stars and exoplanet

masses.  We propose that a series of FGS astrometric observations with

demonstrated 1 millisecond of arc per-observation precision can establish the

degree of coplanarity and component true masses for four extrasolar systems:

HD 202206 (brown dwarf+planet); HD 128311 (planet+planet), HD 160691 = mu Arae

(planet+planet), and HD 222404AB = gamma Cephei (planet+star). In each case

the companion is identified as such by assuming that the minimum mass is the

actual mass. For the last target, a known stellar binary system, the companion

orbit is stable only if coplanar with the AB binary orbit.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11211

Title:                           An Astrometric Calibration of Population II Distance Indicators

PI:                               George Benedict

PI Institution:             University of Texas at Austin

 

In 2002 HST produced a highly precise parallax for RR Lyrae. That measurement

resulted in an absolute magnitude, M(V)= 0.61+/-0.11, a useful result, judged

by the over ten refereed citations each year since. It is, however,

unsatisfactory to have the direct, parallax-based, distance scale of

Population II variables based on a single star. We propose, therefore, to

obtain the parallaxes of four additional RR Lyrae stars and two Population II

Cepheids, or W Vir stars.  The Population II Cepheids lie with the RR Lyrae

stars on a common K-band Period-Luminosity relation. Using these parallaxes to

inform that relationship, we anticipate a zero-point error of 0.04 magnitude.

This result should greatly strengthen confidence in the Population II distance

scale and increase our understanding of RR Lyrae star and Pop II Cepheid

astrophysics.

======================================================================

 

Proposal Category: SNAP

Scientific Category: HOT STARS

ID:                               11212

Title:                           Filling the Period Gap for Massive Binaries

PI:                               Douglas Gies

PI Institution:             Georgia State University Research Foundation

 

The current census of binaries among the massive O-type stars is seriously

incomplete for systems in the period range from years to millennia because the

radial velocity variations are too small and the angular separations too close

for easy detection.  Here we propose to discover binaries in this

observational gap through a Faint Guidance Sensor SNAP survey of relatively

bright  targets listed in the Galactic O Star Catalog.  Our primary goal is to

determine the binary frequency among those in the cluster/association, field,

and runaway groups.  The results will help us assess the role of binaries in

massive star formation and in the processes that lead to the ejection of

massive stars from their natal clusters.  The program will also lead to the

identification of new, close binaries that will be targets of long term

spectroscopic and high angular resolution observations to determine their

masses and distances.  The results will also be important for the

interpretation of the spectra of suspected and newly identified binary and

multiple systems.

======================================================================

 

Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11213

Title:                           Distances to Eclipsing M Dwarf Binaries

PI:                               Gerard van Belle

PI Institution:             California Institute of Technology

 

We propose HST FGS observations to measure accurate distances of 5 nearby M

dwarf eclipsing binary systems, from which model-independent luminosities can

be calculated.  These objects have either poor or no existing parallax

measurements.  FGS parallax determinations for these systems, with their

existing dynamic masses determed to better than 0.5%, would serve as model-

independent anchor points for the low-mass end of the mass-luminosity diagram.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11214

Title:                           HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic

PI:                               John Wisniewski

PI Institution:             NASA Goddard Space Flight Center

 

Beta Pic and AU Mic are two nearby Vega-type debris disk stars.  Both of these

disk systems have been spatially resolved in exquisite detail, predominantly

via the ACS coronagraph and WFPC-2 cameras onboard HST.  These images exhibit

a wealth of morphological features which provide compelling indirect evidence

that these systems likely harbor short-period planetary body(ies).  We propose

to use the superlative astrometric capabilities of HST/FGS to directly detect

these planets, hence provide the first direct planet detection in a Vega-type

system whose disk has been imaged at high spatial resolution.

======================================================================

 

Proposal Category: GO

Scientific Category: QUASAR ABSORPTION LINES AND IGM

ID:                               11215

Title:                           New Sightlines for the Study of Intergalactic Helium: Dozens of High-Confidence, UV-Bright Quasars from SDSS/GALEX

PI:                               Scott Anderson

PI Institution:             University of Washington

 

The reionization of IGM helium is thought to have occurred at redshifts of z=3

to 4. Detailed study of HeII Lyman-alpha absorption toward a handful of QSOs

at 2.7<z<3.3 demonstrated the high potential of such IGM probes, but the

critically small sample size limits confidence in cosmological inferences. The

requisite unobscured sightlines to high-z are extremely rare, but SDSS

provides 5800, z>3.1 QSOs potentially suitable for HeII studies. We've cross-

correlated SDSS quasars with GALEX UV sources to obtain dozens of new, high

confidence, candidate sightlines (z=3.1-4.9) potentially useful for detailed

HeII studies with HST. We propose brief, 2-orbit reconnaissance ACS SBC prism

exposures toward each of the best dozen new quasars, to definitively verify UV

flux down to HeII. Our combined SDSS/GALEX selection insures a high

confirmation rate, as the quasars are already known to be UV bright in GALEX.

Our program will provide a statistical sample of HeII sightlines extending to

high redshift, enabling future long exposure follow-up spectra with the SBC

prism, or superb quality COS or STIS spectra after SM4. Stacks of our prism

spectra will also directly yield ensemble information. Ultimately, the new

sightlines will enable confident measures of the spectrum and evolution of the

ionizing background, the evolution of HeII opacity, the epoch of helium

reionization, and the density of IGM baryons.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11216

Title:                           Monitoring the Giant Flare of HST-1 in the M87 Jet

PI:                               John Biretta

PI Institution:             Space Telescope Science Institute

 

As the nearest galaxy with an optical jet, M87 affords an unparalleled

opportunity to study extragalactic jet phenomena at the highest resolution.

During 2002, HST and Chandra monitoring of the M87 jet detected a dramatic

flare in knot HST-1 located ~1" from the nucleus.  Its optical brightness

eventually increased seventy-fold and peaked in 2005; the X-rays show a

similarly dramatic outburst. In both bands HST-1 is still extremely bright and

greatly outshines the galaxy nucleus. To our knowledge this is the first

incidence of an optical or X-ray outburst from a jet region which is spatially

distinct from the core source -- this presents an unprecedented opportunity to

study the processes responsible for non-thermal variability and the X-ray

emission.  We propose six epochs of HST/WFPC2 flux monitoring during Cycle 16,

as well as seven epochs of Chandra/ACIS observation (5ksec each, six Chandra

epochs contemporary with HST).  At two of the HST/WFPC2 epochs we also gather

spectral information, and at one epoch we will map the magnetic field

structure.  The results of this investigation are of key importance not only

for understanding the nature of the X-ray emission of the M87 jet, but also

for understanding flares in blazar jets, which are highly variable, but where

we have never before been able to resolve the flaring region in the optical or

X-rays.  These new observations will allow us to track the decay phase of the

giant flare, and study smaller secondary flares such as seen late in 2006.

Ultimately we will test synchrotron emission models for the X-ray outburst,

constrain particle acceleration and loss timescales, and study the jet

dynamics associated with this flaring component.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11217

Title:                           The Light Echoes around V838 Monocerotis

PI:                               Howard Bond

PI Institution:             Space Telescope Science Institute

 

V838 Monocerotis, which burst upon the astronomical scene in early 2002, is a

completely unanticipated new object.  It underwent a large-amplitude and very

luminous outburst, during which its spectrum remained that of an extremely

cool supergiant.  A rapidly evolving set of light echoes around V838 Mon was

discovered soon after the outburst, and quickly became the most spectacular

display of the phenomenon ever seen.  These light echoes provide the means to

accomplish three unique types of measurements based on continued HST imaging

during the event:      (1) Study effects of MHD turbulence at high resolution and

in 3 dimensions; (2) Construct the first unambiguous and fully 3-D map of a

circumstellar dust envelope in the Milky Way; (3) Study dust physics in a

unique setting where the spectrum and light curve of the illumination, and the

scattering angle, are unambiguously known. We have also used our HST data to

determine the distance to V838 Mon through direct geometric techniques.

Because of the extreme rarity of light echoes, this is almost certainly the

only opportunity to achieve such results during the lifetime of HST.  We

propose two visits during Cycle 16, in order to continue the mapping of the

circumstellar dust and to accomplish the other goals listed above.

======================================================================

 

Proposal Category: SNAP

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11218

Title:                           Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group

PI:                               Howard Bond

PI Institution:             Space Telescope Science Institute

 

Planetary nebulae (PNe) in globular clusters (GCs) raise a number of

interesting issues related to stellar and galactic evolution.  The number of

PNe known in Milky Way GCs, 4, is surprisingly low if one assumes that all

stars pass through a PN stage.  However, it is likely that the remnants of

stars now evolving in Galactic GCs leave the AGB so slowly that any ejected

nebula dissipates long before the star becomes hot enough to ionize it. Thus

there should not be ANY PNe in Milky Way GCs--but there are four

======================================================================

 

Proposal Category: SNAP

Scientific Category: AGN/QUASARS

ID:                               11219

Title:                           Active Galactic Nuclei in nearby galaxies:         a new view of the origin of the radio-loud radio-quiet dichotomy?

PI:                               Alessandro Capetti

PI Institution:             Osservatorio Astronomico di Torino

 

Using archival HST and Chandra observations of 34 nearby early-type galaxies

(drawn from a complete radio selected sample) we have found evidence that the

radio-loud/radio-quiet dichotomy is directly connected to the structure of the

inner regions of their host galaxies in the following sense:    [1] Radio-loud

AGN are associated with galaxies with shallow cores in their light profiles

[2] Radio-quiet AGN are only hosted by galaxies with steep cusps. Since the

brightness profile is determined by the galaxy's evolution, through its merger

history, our results suggest that the same process sets the AGN flavour. This

provides us with a novel tool to explore the co-evolution of galaxies and

supermassive black holes, and it opens a new path to understand the origin of

the radio-loud/radio-quiet AGN dichotomy.  Currently our analysis is

statistically incomplete as the brightness profile is not available for 82 of

the 116 targets. Most galaxies were not observed with HST, while in some cases

the study is obstructed by the presence of dust features. We here propose to

perform an infrared NICMOS snapshot survey of  these 82 galaxies. This will

enable us to i) test the reality of the dichotomic behaviour in a

substantially larger sample; ii) extend the comparison between radio-loud and

radio-quiet AGN to a larger range of luminosities.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11220

Title:                           Mapping the FUV Evolution of Type IIn Supernovae

PI:                               Jeff Cooke

PI Institution:             University of California - Irvine

 

We will use the PR110L prism on the SBC of ACS to map the FUV evolution of

Type IIn supernovae (SNe).    The main goal of this proposal is to measure the

FUV continuum, Ly-a emission line flux, and their evolution to (1) quantify

and interpret Type IIn SN transient event detections at high redshift and (2)

dramatically improve current high redshift Type IIn selection criteria. We

show that the inherent properties of Type IIn SNe facilitate high redshift

detection.  We will observe the rest-frame FUV of a sample of eight 0.02 < z <

0.33 Type IIn SNe to directly measure the survival of Ly-alpha photons in low

redshift Type IIn SNe environments and extrapolate the results to high

redshift.  We will calibrate relationships such as FUV luminosity vs. emission

line flux and measure emission line evolution vs. FUV light evolution.  The

intent is to categorize and improve the utility of Type IIn SNe.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11221

Title:                           A Dark Core in Abell 520

PI:                               Julianne Dalcanton

PI Institution:             University of Washington

 

We have recently disocovered that the rich cluster Abell 520 exhibits truly

extreme multi-wavelength characteristics. The data indicate that the cluster

is the site of a major merger. Our weak lensing analysis, based on a deep CFHT

image, suggests the presence of a massive dark core that coincides with the

central X-ray emission peak, while being largely devoid of galaxies. Although

a displacement between the X-ray gas and the galaxy/dark matter distribution

may be expected in a merger (e.g. as in the bullet cluster), the dark matter

peak without galaxies cannot be easily explained within the current

collisionless dark matter paradigm. A higher resolution mass map is required

to make further progress, as it will enable us to examine the detailed

structure of the dark matter distribution, as well as improve the significance

of the dark peak. We propose a 3 x 3 WFPC2 mosaic of interlaced images, where

each pointing consists of two sets of F814W exposures offset by 5.5 pixels.

This will precisely pinpoint the locations of the highest lensing peaks,

enhance the comparison with the Chandra X-ray data, and test physical and

geometrical models for the spatial and thermal structure of this remarkable

cluster derived from our suite of gas+dark matter simulations of head-on/off-

axis cluster mergers.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11222

Title:                           Direct Detection and Mapping of Star Forming Regions  in Nearby, Luminous Quasars

PI:                               Michael Eracleous

PI Institution:             The Pennsylvania State University

 

We propose to carry out narrow-band emission line imaging observations of

seven quasars at z=0.05-0.09 with the WFPC2 ramp filters and with the NICMOS

narrow-band filters. We will obtain images in the [O II], [O III], H-beta, and

Pa-alpha emission line bands to carry out a series of diagnostic tests aimed

at detecting and mapping out star-forming regions in the quasar host galaxies.

This direct detection of star-forming regions will confirm indirect

indications for star formation in quasar host galaxies. It will provide a

crucial test for models of quasar and galaxy evolution, that predict the co-

existence of starbursts and "monsters" and will solve the puzzle of why

different indicators of star formation give contradictory results. A secondary

science goal is to assess suggested correlations between quasar luminosity and

the size of the narrow-line region.

======================================================================

 

Proposal Category: GO

Scientific Category: COOL STARS

ID:                               11223

Title:                           The Key to Understanding RR Lyr Stars:            WFPC2 Observations of a Unique LMC EB with a RR Lyr Component

PI:                               Edward Guinan

PI Institution:             Villanova University

 

We are proposing HST/WFPC2 2550-10420A multi-band photometry of an important

"unique" LMC eclipsing binary with an RR Lyr component. This binary is the

only bona fide eclipsing binary (EB) with an RR Lyr component. Because of

their constant mean luminosities (L ~ 45 Lsun; <Mv> ~ +0.5 mag) and easily

recognizable light curves, RR Lyr variables have long served as the

"cornerstone" of the Pop II distance scale in our galaxy and for Local Group

galaxies. However, in spite of their critical importance to astronomy, there

is a paucity of fundamental data available for RR Lyr stars. In fact, there

are no direct measures of their most fundamental properties - such as Mass,

Radius and Luminosity. The astrophysical and cosmological consequences of

finding an RR Lyr star in an EB are considerable, because the masses and

absolute radii of the stars of eclipsing binaries can be determined to within

a few percent from time-tested analyses of their light and radial velocity

curves. With accurate temperatures and ISM absorption values, determined from

the proposed WFPC2 observations, it is possible to determine reliable stellar

luminosities and distances. It is for these reasons that we propose WFPC2

observations of the recently discovered detached LMC eclipsing binary OGLE

J052218.07-692827.4 (<V> ~18.6-mag; <B-V>0 ~+0.27; Porb = 8.9231-d); the RR

Lyr primary component has a pulsation period of P(RR) = 0.564876-d. This

important binary star is an integral part of our on-going multi-wavelength

study of selected eclipsing binaries in nearby galaxies. Three HST/WFPC2

orbits are requested to determine complementary accurate Teff, log g and ISM

absorption (A-lambda) for the component stars. These quantities will be

combined with the fundamental stellar data being determined from our ground-

based radial velocity and photometric observations. The combined observations

will yield accurate stellar masses, radii, temperatures and luminosities, as

well as a direct distance to the binary and LMC-Bar. This RR Lyr/EB thus

offers the unprecedented opportunity to:            (1) determine directly (and for the

first time) the fundamental physical properties (M, R, L) of an RR Lyr star,

(2) directly calibrate "in situ" the zero-point of the LMC RR Lyr - P - Mv - Z

relation and (3) to derive an additional accurate distance to the Bar region

of the LMC.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11224

Title:                           Unraveling Mira AB Accretion Mysteries

PI:                               Margarita Karovska

PI Institution:             Smithsonian Institution Astrophysical Observatory

 

Wind accretion is one of the most common yet poorly understood phenomena in

astrophysics. A  key step toward advancing our understanding of physical

processes and accretion geometries in wind accreting systems is direct imaging

of the individual components and mass flows. The nearby symbiotic binary Mira

AB, composed of an AGB donor star and an accreting compact companion,  is a

unique target  since it can be easily spatially resolved with the HST, and

thus serves as a perfect test laboratory for accretion studies in wind

interacting systems.  We propose to carry out WFPC2 observations of Mira AB

following the HST and Chandra detections of an unprecedented outburst from the

cool giant, and the discovery of an accretion stream showing for the first

time evidence for a direct mass transfer between the components in a wind

accreting system. High-angular-resolution multiwavelength imaging at UV

/optical wavelengths will allow us to determine the properties of the ejected

material as it flows throughout the binary and interacts with the Mira A

circumstellar material and wind; the physical characteristics of mass transfer

in this system and especially the role of the accretion stream between Mira A

and Mira B; and the response of the system to the increased accretion rate

onto Mira B following the outburst.  These results will provide crucial inputs

and quantitative constraints to models of wind interacting systems and will

also anchor our understanding of accretion processes in a wide range of

interacting binaries that cannot be currently resolved, including in other

symbiotics and more exotic systems such as accreting black holes and neutron

stars in high-mass X-ray binaries.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11225

Title:                           The Wavelength Dependence of Accretion Disk Structure

PI:                               C. Kochanek

PI Institution:             The Ohio State University Research Foundation

 

We can now routinely measure the size of quasar accretion disks  using

gravitational microlensing of lensed quasars.  The next  step to testing

accretion disk models is to measure the size  of accretion disks as a function

of wavelength, particularly  at the UV and X-ray wavelengths that should probe

the inner,  strong gravity regime.  Here we focus on two four-image quasar

lenses that already have optical (R band) and X-ray size  measurements using

microlensing.  We will combine the HST observations with ground-based

monitoring to measure the  disk size as a function of wavelength from the

near-IR to the UV.   We require HST to measure the image flux ratios in the

ultraviolet continuum near the Lyman limit of the quasars. The selected

targets have estimated black hole masses  that differ by an order of

magnitude, and we should find wavelength  scalings for the two systems that

are very different because  the Blue/UV wavelengths should correspond to parts

of the disk  near the inner edge for the high mass system but not in the  low

mass system.  The results will be modeled using a combination of simple thin

disk models and complete relativistic disk models. While requiring only 18

orbits, success for one system requires  observations in both Cycles 16 and

17.

======================================================================

 

Proposal Category: GO

Scientific Category: SOLAR SYSTEM

ID:                               11226

Title:                           Hubble Investigation of Comet 8P/Tuttle

PI:                               Philippe Lamy

PI Institution:             Laboratoire d'Astrophysique de Marseille

 

Comet 8P/Tuttle is a returning nearly isotropic comet (NIC) with an

outstanding apparition in cycle 16, passing within 0.25 AU of the Earth. We

propose a 12-orbit Hubble investigation that will allow us to determine the

size, shape, rotational period, and color (UBVRI) of 8P, thereby providing the

most detailed view of a NIC nucleus since the spacecraft flyby of 1P/Halley in

1986. The return of 8P is a rare opportunity, and we expect many other

observatories, including Spitzer, to be investigating this comet. Combining

the Hubble results with those  from other observatories should yield a

comprehensive picture of this NIC that can be compared to the detailed data

collected on ecliptic comets (ECs) during the past 3 decades. The differences

and similarities between NICs and ECs should yield valuable insights into the

origin and evolution of comets.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11227

Title:                           The orbital period for an ultraluminous X-ray source in NGC1313

PI:                               Jifeng Liu

PI Institution:             Smithsonian Institution Astrophysical Observatory

 

The ultraluminous X-ray sources (ULXs) are extragalactic point sources with

luminosities that exceed the Eddington luminosity for conventional stellar-

mass black holes by factors of 10 - 100.  It has been hotly debated whether

the ULXs are just common stellar-mass black hole sources with beamed emission

or whether they are sub-Eddington sources that are powered by the long-sought

intermediate mass black holes (IMBH).  To firmly decide this question, one

must obtain dynamical mass measurements through photometric and spectroscopic

monitoring of the secondaries of these system.  The crucial first step is to

establish the orbital period of a ULX, and arguably the best way to achieve

this goal is by monitoring its ellipsoidal light curve.  The extreme ULX

NGC1313 X-2 provides an outstanding target for an orbital period determination

because its relatively bright optical counterpart (V = 23.5) showed a 15%

variation between two HST observations separated by three months.  This level

of variability is consistent with that expected for a tidally distorted

secondary star.  Here we propose a set of 20 imaging observations with

HST/WFPC2 to define the orbital period.  This would be the first photometric

measurement of the orbital period of a ULX binary. Subsequently, we will

propose to obtain spectroscopic observations to obtain its radial velocity

amplitude and thereby a dynamical estimate of its mass.

======================================================================

 

Proposal Category: GO

Scientific Category: STAR FORMATION

ID:                               11228

Title:                           Extrasolar Planet XO-2b

PI:                               Peter McCullough

PI Institution:             Space Telescope Science Institute

 

We propose observations of the newly discovered extrasolar planet XO-2b and

its twin star XO-2. When combined with the transit light curve, the FGS-

derived parallax will constrain the stellar mass of the host star XO-2. From

the high signal-to-noise near-IR time series resulting from NICMOS grism

spectroscopy, we will refine the system parameters, in particular radii of the

star and planet. From the same data, we will search for evidence of water

vapor in the atmosphere via transmission spectroscopy. Differential

observations with NICMOS in the spectroscopic mode will be used to search for

the small spectral changes that occur during planetary transits resulting from

absorption of stellar light as it passes through the planetary atmosphere.

Water is an important constituent, the detection of which would provide

information on Oxygen, and it has a convenient strong band well-positioned for

NICMOS.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11229

Title:                           SEEDS:         The Search for Evolution of Emission from Dust in Supernovae with HST and Spitzer

PI:                               Margaret Meixner

PI Institution:             Space Telescope Science Institute

 

The role that massive stars play in the dust content of the Universe is

extremely uncertain.  It has long been hypothesized that dust can condense

within the ejecta of supernovae (SNe), however there is a frustrating

discrepancy between the amounts of dust found in the early Universe, or

predicted by nucleation theory, and inferred from SN observations. Our SEEDS

collaboration has been carefully revisiting the observational case for dust

formation by core-collapse SNe, in order to quantify their role as dust

contributors in the early Universe.  As dust condenses in expanding SN ejecta,

it will increase in optical depth, producing three  simultaneously observable

phenomena: (1) increasing optical extinction; (2) infrared (IR) excesses; and

(3) asymmetric blue-shifted emission lines. Our SEEDS collaboration recently

reported all three phenomena occuring in SN2003gd, demonstrating the success

of our observing strategy, and permitting us to derive a dust mass of up to

0.02 solar masses created in the SN. To advance our understanding of the

origin and evolution of the interstellar dust in galaxies, we propose to use

HST's WFPC2 and NICMOS instruments plus Spitzer's photometric instruments to

monitor ten recent core-collapse SNe for dust formation and, as a bonus,

detect light echoes that can affect the dust mass estimates. These space-borne

observations will be supplemented by ground-based spectroscopic monitoring of

their optical emission line profiles. These observations would continue our 2-

year HST and Spitzer monitoring of this phenomena in order to address two key

questions:     Do all SNe produce dust? and How much dust do they produce?  As all

the SN are witin 15 Mpc, each SN stands an excellent chance of  detection with

HST and Spitzer and of resolving potential light echoes.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11230

Title:                           HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution

PI:                               Christopher O'Dea

PI Institution:             Rochester Institute of Technology

 

The intracluster medium (ICM)  now appears to be a very dynamic place where

heating and cooling processes vie for dominance and an uneasy equilibrium is

maintained. Since these same processes may operate during the process of

galaxy formation, the centers of clusters of galaxies provide low redshift

laboratories for studying the critical processes involved in galaxy formation

and black hole growth. At the present time, the main questions are (1) How

much gas is cooling out of the ICM? (2) How much star formation is ongoing?

(3) What is the impact of the gas and star formation on the central BCG? In

order to measure the current star formation in BCGs we have undertaken a

program of Spitzer IRAC and MIPS observations. We are in process of obtaining

observations of a sample of Brightest Cluster Galaxies in 70 clusters selected

from the ROSAT all sky survey. In about 25% of the sources observed so far, we

detect a mid-IR excess which we attribute to dust heated by star formation. We

propose to obtain ACS/SBC observations of the Lyman Alpha emission line and

the adjacent FUV continuum in 7 BCGs which are in cooling core clusters of

galaxies and have a large mid-IR excess. We also propose WFPC2 F606W

observations of the two clusters without high resolution imaging to allow us

to image the dust on the same scale as the Far UV continuum. The FUV will

allow us to confirm the presense of ongoing starformation in these BCGs and

will allow us to rule out an AGN as the dominant contributer to the mid-IR.

The morphology and spatial extent of the young stars and the heated dust and

CO will constrain the spatial scale over which star formation occurs and thus

where the  cooling gas is deposited. The combination of our FUV and IR

observations will allow us to estimate the star formation rates which  must

balance the rate at which cold gas is deposited in the BCG. Our proposed FUV

observations will produce unique information about the cooling gas, the true

mass accretion rates, and the star formation rates in BCGs and its effect on

the galaxy.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11231

Title:                           Calibration of the WFPC2 HeII and [SII] Filters.

PI:                               C. O'Dell

PI Institution:             Vanderbilt University

 

Observations of NGC 6720 (the Ring Nebula) will be used to determine the

calibration constants for the important emission-line filters that isolate

nebular HeII (F469N) and [SII] (F673N) emission. The pre-launch calibrations

are inadequate because of possible temporal changes and the fact that these

interference filters are used in a different configuration from that of the

ground calibration. The Ring Nebula is a nearly ideal reference source as

multiple 2.4"x4.0" samples have been accurately measured spectro-

photometrically and five of the six samples can be imaged with one pointing of

the HST.  The method of derivation of the calibration constants will be the

same as previously employed to calibrate the primary emission-line filters for

the WFPC2 (F487N, F502N, F656N, F658N) and ACS (F502N, F658N, F660N) using the

Orion Nebula as a reference source. However, Orion cannot be used for this

calibration because the targeted lines are weak ([SII]) or absent (HeII) and

the scattered-light continuum is strong. The Ring Nebula has strong HeII

emission in its middle, strong [SII] emission in its main ring, and a weak

(atomic only) continuum.

======================================================================

 

Proposal Category: GO

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11232

Title:                           Determination of Angular Expansion Velocities in the Ring Nebula

PI:                               C. O'Dell

PI Institution:             Vanderbilt University

 

The Ring Nebula (NGC 6720) represents an important stage in the evolution of

planetary nebulae, being large enough that it has entered the post fast-wind

stage yet has not reached the late ballistic phase of objects like the Helix

Nebula. Understanding this nebula well presents the opportunity to determine

how nebulae transition from their creation phase into the form they have as

their material enters the interstellar medium.  A recent study based on

ground-based spectroscopy has derived a new and accurate model for the Ring

Nebula. A well defined characteristic of this model is that it predicts a

tangential velocity of 20 km/s whereas the application of its quite uncertain

trigonometric parallax distance of 700 (+450/-200) pc with the angular

expansion velocity determined from HST observations with a 2 year time base

indicates a tangential velocity of 69 (+45/-20) km/s. This disagreement

indicates that either the distance is even more uncertain than thought or that

the earlier angular velocity is incorrect.  We propose to make a new set of

observations of the Ring Nebula in the diagnostic emission line filters F469N

(HeII), F502N ([OIII]), and F658N ([NII]) that will produce much more accurate

angular velocities than the previous study by having a time base of 8.8 years

and imaging the nebula entirely within a single CCD of the WFPC2. The primary

result from this study will be an accurate distance to this important nebula

and from this to be able to use this object to refine our picture of how

planetary nebulae evolve during middle-age.

======================================================================

 

Proposal Category: GO

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11233

Title:                           Multiple Generations of Stars in Massive Galactic Globular Clusters

PI:                               Giampaolo Piotto

PI Institution:             Universita di Padova

 

This is a follow-up to recent HST imaging of NGC 2808, which discovered that

its main sequence is triple, with three well-separated parallel branches

(Fig.~1).   Along with the double MS of Omega Centauri, this challenges the

long-held paradigm that globular clusters are simple, single stellar

populations.  The cause of this main sequence multiplicity in both clusters is

likely to be differences in helium abundance, which could play a fundamental

role in the understanding of stellar populations. We propose to image seven

more of the most massive globular clusters, to examine their main  sequences

for indications of splitting.

======================================================================

 

Proposal Category: GO

Scientific Category: HOT STARS

ID:                               11234

Title:                           A Brief Revisit of the Crab

PI:                               Roger Romani

PI Institution:             Stanford University

 

We propose using WFPC2 to obtain continuum-dominated images of the Crab pulsar

and environs closely duplicating archival exposures from 1994 and 1995. By

matching the archival data we can realize ~3mas precision astrometry with a

minimum of systematic effects over a maximum (~13.5y) baseline.  This

determines the Crab proper motion to better than 0.3mas/yr (3km/s) accuracy

and measures its position angle to better than 1.5degrees, i.e. reducing the

errrors of the best present (HST archive) measurement by a factor of three.

Most importantly, this provide a nearly systematic-free result. This proper

motion measurement would match the precision of the CXO-measured angular

momentum vector. Comparison of these vectors is the foundation of an effort to

understand the physical origin of the large momentum kick at pulsar birth.

======================================================================

 

Proposal Category: GO

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11235

Title:                           HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies in the Local Universe

PI:                               Jason Surace

PI Institution:             California Institute of Technology

 

At luminosities above 10^11.4 L_sun, the space density of far-infrared

selected galaxies exceeds that of optically selected galaxies. These `luminous

infrared galaxies' (LIRGs) are primarily interacting or merging disk galaxies

undergoing enhanced star formation and Active Galactic Nuclei (AGN) activity,

possibly triggered as the objects transform into massive S0 and elliptical

merger remnants. We propose NICMOS NIC2 imaging of the nuclear regions of a

complete sample of 88 L_IR > 10^11.4 L_sun luminous infrared galaxies in the

IRAS Revised Bright Galaxy Sample (RBGS:    i.e., 60 micron flux density > 5.24

Jy). This sample is ideal not only in its completeness and sample size, but

also in the proximity and brightness of the galaxies. The superb sensitivity

and resolution of NICMOS NIC2 on HST enables a unique opportunity to study the

detailed structure of the nuclear regions, where dust obscuration may mask

star clusters, AGN and additional nuclei from optical view, with a resolution

significantly higher than possible with Spitzer IRAC. This survey thus

provides a crucial component to our study of the dynamics and evolution of IR

galaxies presently underway with Wide-Field, HST ACS/WFC and Spitzer IRAC

observations of these 88 galaxies. Imaging will be done with the F160W filter

(H-band) to examine as a function of both luminosity and merger stage (i) the

luminosity and distribution of embedded star clusters, (ii) the presence of

optically obscured AGN and nuclei, (iii) the correlation between the

distribution of 1.6 micron emission and the mid-IR emission as detected by

Spitzer IRAC, and (iv) the evidence of bars or bridges that may funnel fuel

into the nuclear region. The NICMOS data, combined with the HST ACS, Spitzer,

and GALEX observations of this sample, will result in the most comprehensive

study of merging and interacting galaxies to date.

======================================================================

 

Proposal Category: GO

Scientific Category: COSMOLOGY

ID:                               11236

Title:                           Did Rare, Large Escape-Fraction Galaxies Reionize the Universe?

PI:                               Harry Teplitz

PI Institution:             California Institute of Technology

 

Lyman continuum photons produced in massive starbursts may have played a

dominant role in the reionization of the Universe. Starbursts are important

contributors to the ionizing metagalactic background at lower redshifts as

well. However, their contribution to the background depends upon the fraction

of ionizing radiation that escapes from the intrinsic opacity of galaxies

below the Lyman limit. Current surveys suggest that the escape fraction is

close to zero in most galaxies, even among young starbursts, but is large in

15-25% of them.  Non-uniform escape fractions are expected as a result of

violent events creating clear paths in small parts of galaxies.  The number of

galaxies observed with high escape fraction will result from the combination

of the intrinsic number with clear lines of sight and their orientation with

respect to the observer.   We propose to measure the fraction of escaping

Lyman continuum radiation in a large sample (47) of z~0.7 starbursts in the

COSMOS field.  These compact UV-lumnious galaxies are good analogs to high

redshift LBGs. Using the SBC/PR130L we can quickly (1-4 orbits) detect

relative escape fractions (f_LC/f_1500) of 25% or more.  This will be the

first measurement of the escape fraction in sources between z=1 and the local

universe.  We expect ~10 detections.  Stacking  will set limits of <4% on the

relative escape fraction in the rest.  We will correlate the LC detections

with the properties of the galaxies.  By targetting z~0.7 in COSMOS, we will

have tremendous ancillary information on those sources.  A non-detection in

all sources would be significant (99% confidence).  This would imply that QSOs

provide the overwhelming majority of ionizing radtion at z<1, requiring

substantial evolution in the processes within Lyman break galaxies which allow

large escape fractions at high redshift.

======================================================================

 

Proposal Category: GO

Scientific Category: AGN/QUASARS

ID:                               11237

Title:                           The origin of the break in the AGN luminosity function

PI:                               Lutz Wisotzki

PI Institution:             Astrophysikalisches Institut Potsdam

 

We propose to use NICMOS imaging to measure rest-frame optical luminosities

and morphological properties of a complete sample of faint AGN host galaxies

at redshifts z ~ 1.4. The targets are drawn from the VLT-VIMOS Deep Survey,

and they constitute a sample of the lowest luminosity type 1 AGN known at z >

1. The spectroscopically estimated black hole masses are up to an order of

magnitude higher than expected given their nuclear luminosities, implying

highly sub-Eddington accretion rates. This exactly matches the prediction made

by recent theoretical models of AGN evolution, according to which the faint

end of the AGN luminosity function is populated mainly by big black holes that

have already exhausted a good part of their fuel.  In this proposal we want to

test further predictions of that hypothesis, by focussing on the host galaxy

properties of our low-luminosity, low-accretion AGN. If the local ratio

between black hole and bulge masses holds at least approximately at these

redshifts, one expects most of these low-luminosity AGN to  reside in fairly

big ellipticals with stellar masses around and above 10^11 solar masses (in

contrast to the Seyfert phenomenon in the local universe). With NICMOS imaging

we will find out whether that is true, implying also a sensitive test for the

validity of the M_BH/M_bulge relation at z ~ 1.4.

======================================================================

 

Proposal Category: AR

Scientific Category: COOL STARS

ID:                               11238

Title:                           Searching For Unresolved Binary Brown Dwarfs Using Point Spread Functions

PI:                               Jacob Albretsen

PI Institution:             Brigham Young University

 

There currently are objects of L and T spectral type with errors in their

classification of +/- 1 to 2.  Metallicity and gravitational differences have

accounted for some of these discrepancies, and recent studies have shown

unresolved binary brown dwarfs may offer some explanation as well.  However

limitations in technology and resources make it difficult to clearly resolve

an object that may be binary in nature.  It has been shown that using model

point-spread functions for single and binary sources have been able to

identify statistically strong binary candidates from images that are

apparently unresolved.   The HST archive contains numerous observations of

brown dwarfs from NICMOS that have never been rigorously analyzed for binary

properties.   Results from for this archive proposal will help determine if

there really is an increase in binary brown dwarfs in the L/T transition and

identify potential candidates for future observations to determine orbital

information.

======================================================================

 

Proposal Category: AR

Scientific Category: COOL STARS

ID:                               11239

Title:                           Identifying Atomic and Molecular Absorption in an Extrasolar Planet Atmosphere

PI:                               Travis Barman

PI Institution:             Lowell Observatory

 

A significant amount of Hubble Space Telescope time has been spent observing a

normal bright main-sequence star, HD209458, which happens to also be home to

one of the few transiting extrasolar planets.  Time-series spectroscopic data

taken with STIS and ASC are available in the archive covering numerous

planetary transits over the past 7 years.  These data have allowed the

discovery of sodium absorption in HD209458b's atmosphere along with a

hydrogen-rich extended exosphere.  There is great potential for significant

new discoveries with these data that could further constrain the chemical

composition and chemical evolution of HD209458b.  This proposal outlines steps

toward improving our understanding of the chemical composition of extrasolar

giant planet atmospheres by developing new models for the wavelength-dependent

eclipse depth that may be directly compared to archival Hubble Space Telescope

observations.

======================================================================

 

Proposal Category: AR

Scientific Category: STAR FORMATION

ID:                               11240

Title:                           Mass Loss From Hot Jupiters

PI:                               Eugene Chiang

PI Institution:             University of California - Berkeley

 

Photoionization heating from UV radiation incident on the atmospheres of hot

Jupiters drives planetary mass loss in the form of hydrodynamic winds.  HST

STIS observations of HD 209458b, the first hot Jupiter discovered to transit

its host star, have confirmed that the planet is losing atomic hydrogen

(Vidal-Madjar et al. 2003) and have suggested that it may be losing OI and CII

(Vidal-Madjar et al. 2004).  These observations, which can be repeated with

the advent of the HST Cosmic Origins Spectrograph (COS), do not necessarily

imply loss of gas at a rate large enough to significantly reduce the mass of

the planet.  HST STIS observations indicating a population of hydrogen in the

n=2 state constrain the structure of the planet's escaping atmosphere

(Ballester et al.~2007).  We propose to construct a model of mass loss from

hot Jupiter atmospheres, including realistic heating and cooling, ionization

balance, tidal gravity, and pressure-confinement by the stellar wind.  We have

already constructed a model that resolves the atmosphere's transition from

atomic to ionized hydrogen.  In our proposed work, we plan to also resolve the

transition from molecular to atomic hydrogen.  We will employ ray-tracing

through our model to explain the HST STIS detections of Lyman alpha and Balmer

continuum absorption by neutral hydrogen in an extended atmosphere around HD

209458b, and we will experiment with metal chemistry and vertical mixing in an

attempt to reproduce the HST STIS measurement of OI and CII.  Our work will

provide predictions for future COS measurements.  We will infer the correct

mass loss rate implied by the Vidal-Madjar et al. (2003) observation and

search for new observational diagnostics of hot Jupiter atmospheres.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11241

Title:                           IR Background Fluctuations in NICMOS Ultra and Hubble Fields and the Surface Density of First-Light Galaxies

PI:                               Asantha Cooray

PI Institution:             University of California - Irvine

 

We propose an archival analysis of F160W and F110W NICMOS Ultra Deep Field

(NUDF) and Hubble Deep Field North (HDFN) data, combined with deep HST ACS

images of the same field, to measure clustering of unresolved IR background

(IRB) present in  "empty" pixels. These clustering measurements will be used

to study any indications for the presence of an unresolved, diffuse IR

background from redshifts related to reionization and associated with

redshifted UV emission from first-light galaxies and Lyman-alpha emission from

recombinations in surrounding HII halos. The IR background from these sources

are expected to peak at wavelengths between 1 and 2 microns and it's

fluctuations have a clustering spectrum distinctively different from that of

low-redshift faint galaxies. We will account for the confusion from latter

with ACS detections of faint blue optical galaxies with no IR counterparts in

NICMOS images. We will cross-correlate unresolved IR fluctuations between

F110W and F160W images of the same field to determine any wavelength

dependence of the IR background and to separate various noise and systematic

effects which are not common to both passbands. We will simulate to estimate

the noise floor generated by residual flat-field errors and the pedestal

effect involving varying bias in different quadrants of the NICMOS array. For

IR anisotropy power spectrum measurements, we will borrow and implement well

established techniques used with cosmic microwave background (CMB) anisotropy

maps by the CMB community. At a wavelength of 1.25 microns, DIRBE indicates a

total IRB intensity of 54 +/- 17 nW/m^2/sr or 28 +/- 15 nW/m^2/sr, while about

8 nW/m^2/sr comes from known galaxy counts. Our clustering measurements,

combined with analytical and numerical models, will lead to a detection of the

total IRB intensity from first-light galaxies containing Pop III stars during

reionization as low as 3 nW/m^2/sr. A direct estimate on the integrated

intensity, and thus the surface density of first-light galaxies, from

unresolved IR fluctuations has strong consequences for imaging searches for

high-redshift Lyman-alpha emitters and for models of galaxy formation and

evolution.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11242

Title:                           IR Background Intensity, Anisotropy, and Lyman-alpha Sources in Large Volume Simulations of Reionization

PI:                               Asantha Cooray

PI Institution:             University of California - Irvine

 

We propose to analyze properties of the UV photon background emitted by

reionizing sources redshifted to IR wavelngths today in a set of large volume,

(100 Mpc)^3, high resolution  simulations (24 billion particles) of the cosmic

reionization process. Using these cosmological simulations, we will establish,

for the first time,  the expected IR background intensity at wavelengths

between ~1 micron and ~4 microns as well as the anisotropy power spectrum of

fluctuations observable with NICMOS F110W/F160W bands and WFC3 IR bands. The

new hybrid code for reionization simulations developed at Princeton by CoIs

Cen & Trac includes an adaptive ray tracing algorithm for radiative transfer

of ionizing photons from first-light galaxies containing both population II

and population III stars. Fluctuation studies of the unresolved intensity in

deep IR images, including those with NICMOS, have shown an excess anisotropy

contribution above noise when resolved sources down to very faint flux levels

are masked out. This excess has been described as a signature of first

galaxies containing Pop III stars. While fluctuation measurements have not

conclusively established the presence of Pop III stars,  we do expect

unresolved IR background to fluctuate due to clustering of  first-light

sources.  Given differences in model assumptions, analytical predictions on

the fluctuation strength vary widely in the literature, while numerical

simulations of reionization have not been used to study IR background

statistics. These will be compared to existing measurements and to establish

requirements (depth, area) for a WFC3 survey to measure statistics of first

galaxies. We will investigate how color information, in terms of fluctuation

amplitude ratios of IR bandpasses of NICMOS and WFC3, can be used to study the

redshift duration of reionization. Simulations will be used to update number

counts, luminosity functions, and clustering of Lyman-alpha sources, and to

compare with recent measurements of Lyman-alpha source statistics at z > 6 by

taking into account of sample variance within the ~1 degree^2 field provided

by simulations. Simulations will also be used to study the transition between

dominant Pop III to dominant Pop II starformation, and any observable

signatures. In addition to results in peer-reviewed publications, simulation

outputs in the form of Lyman-alpha source maps at various passbands of both

NICMOS and WFC3 will be made available publicly on the web within a year of

beginning this research.

======================================================================

 

Proposal Category: AR

Scientific Category: AGN/QUASARS

ID:                               11243

Title:                           Determining the Inclinations of AGN using Narrow-Line Region Kinematics

PI:                               D. Crenshaw

PI Institution:             Georgia State University Research Foundation

 

We will determine the inclinations of the AGN in 36 Seyfert galaxies with STIS

G430M and/or G430L long-slit spectra, by measuring radial velocities as a

function of position in their narrow-line regions (NLRs) and generating

kinematic models to match the observed radial velocities. Our previous studies

of three Seyfert galaxies with STIS show that the kinematics of their NLRs are

dominated by radial outflow, and that simple biconical outflow models can be

used to derive the inclination of the bicone axis, and hence the obscuring

torus, with respect to our line of sight. The inclinations will be compared

with those from other techniques (water masers, broad Fe K-alpha profiles) to

test for discrepancies and identify possible misalignments between the

accretion disk, torus, and/or host galaxy. More importantly, our results will

provide the foundation for future studies that investigate the dependence of

observed properties (e.g., SEDs, absorbing columns, broad-line widths) on

inclination, which is vital for understanding the physics of AGN.

======================================================================

 

Proposal Category: AR

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11244

Title:                           WFPC2 CTE and Photometric Zero Points

PI:                               Andrew Dolphin

PI Institution:             Raytheon Company

 

With charge-transfer efficiency (CTE) losses of several tenths of a magnitude

in many current exposures, the accuracy of CTE corrections is a limiting

factor in the accuracy of photometry that can be obtained with WFPC2.

However, the CTE corrections in common use are five years old, and thus

corrections for CTE loss on current observations are made with the dangerous

assumption that CTE loss has continued growing over the past five years at the

rate it grew for the instruments first eight years of service.  The

uncertainty caused by this assumption implies that the use of these old CTE

corrections is the dominant error source in many WFPC2 images, and will become

even worse in Cycle 16 as the extrapolation increases.  This proposal seeks to

remedy this situation by undertaking an examination of CTE using data of the

Omega Cen calibration field obtained over the entire lifetime of WFPC2.  The

methodology has been proven to produce accurate CTE corrections (indeed, they

are the recommended corrections in the WFPC2 handbook and online CTE

calculator).

======================================================================

 

Proposal Category: AR

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11245

Title:                           Mining the Rich Archive for 47 Tucanae

PI:                               Peter Edmonds

PI Institution:             Eureka Scientific Inc.

 

We propose to capitalise on the extensive set of scientific and calibration

observations of the remarkable globular cluster 47 Tuc.  The chief goals are:

(1) to address key questions about the binaries found in this massive cluster,

including studies of cataclysmic variables (CVs), low-mass X-ray binaries

(LMXBs), millisecond pulsars (MSPs) and chromospherically active binaries, and

(2) to study a dynamically important but thus far neglected class of binaries,

containing subgiant and giant stars. We plan to make the most extensive

analysis to date of long-term variability in globular cluster binaries,

including searches for dwarf nova outbursts, high and low states and periodic

variations for CVs; study accretion rate changes for LMXBs; study active

binaries that appear to undergo coronal mass ejections; identify the nature of

two binaries that experience incredibly bright X-ray flares; confirm new

candidates of rare MSPs with main sequence companions; search for optical IDs

of unidentified Chandra sources. This is the richest population of binaries

known in any globular cluster and the complete archival dataset is unlikely to

be rivaled for many years.  These studies will add to our understanding of

this important crash-test laboratory and have broader implications for stellar

dynamics, stellar and binary evolution and globular cluster evolution.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11246

Title:                           Evolution in the Dark Matter Properties of Strong Lenses through Weak Lensing

PI:                               Christopher Fassnacht

PI Institution:             University of California - Davis

 

To fully exploit the information on the dark matter mass profiles of galaxies

gained from weak lensing and to tie this to their inner regions where baryons

play an important role, we propose to investigate a special sample of

galaxies, namely strong gravitational lenses.  These systems are excellent

targets for weak lensing studies because the Einstein ring radii provide a

direct measurement of the projected mass at very small scales -- information

that is not available for most galaxy samples.  This project is especially

well suited for an archival program because nearly every strong lens system

has been imaged with HST, and the data are public.  What makes this project

stand out is that we can compare strong lens samples at moderate redshift

(median z ~ 0.6) and lower redshift (median z ~ 0.2) and can, thus, use the

full power of combining strong and weak lensing in our investigation of

evolutionary effects over this timescale.  We will use our samples to (1)

measure the average mass profile of the sample to R ~ 300 kpc/h, (2) quantify

the evolution of stellar mass and virial mass-to-light ratios, and (3)

investigate whether the ``bulge-halo conspiracy'', whereby the CDM profiles of

galaxies are NFW but the total (baryonic plus CDM) mass profile are isothermal

out to ~ 300 kpc/h, is in place at higher redshifts.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11247

Title:                           Light Element Nucleosynthesis through Measurements of Interstellar Boron

PI:                               Steven Federman

PI Institution:             University of Toledo

 

With the aim of identifying the sources of light element  (Li, Be, B, and F)

synthesis, we propose a survey of interstellar boron. The B II line at 1362 A

will be used to extract the B column density along more than fifty sight

lines, many of which are associated with regions of massive star formation

shaped by core-collapse supernovae (SNe II).  HST spectra are the only means

for determining the elemental B abundance for sources outside the solar

system. The survey will contain directions that are both molecule poor and

molecule rich, thereby enabling us to examine the overall level of boron

depletion onto grains as a function of gas density. Both the average density

of neutral material along the line of sight and the density inferred from the

fraction of neutral gas in molecular form will be incorporated into the

analysis. We will seek sight lines with B abundances enhanced over the value

seen in regions with the least depletion; such enhancements mainly arise from

recent production of B-11. The boron column density, with the fluorine column

density obtained from archival FUSE spectra of the F I line at 954 A, will

give the B/F abundance ratio. This ratio is a diagnostic of the importance of

neutrino-induced spallation in SNe II in effecting synthesis of B and F, a

process for which direct observational evidence is still lacking.

======================================================================

 

Proposal Category: AR

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11248

Title:                           The Local Environments of Supernovae

PI:                               Alex Filippenko

PI Institution:             University of California - Berkeley

 

The locations of supernovae (SNe) in the local stellar and gaseous environment

in galaxies, as measured in high spatial resolution WFPC2 and ACS images,

contain important clues to their progenitor stars. They provide accurate

determinations of any association of SNe with H II regions or star clusters.

Since multi-filter observations are generally available, we can determine the

local stellar population, setting constraints on the mass of the progenitor;

we can also search for possible attenuation of the SN by dust in the host

galaxy by studying the colors of the stars in its environment. By checking the

fields for background sources, we can correct the existing SN light curves and

luminosities if necessary. When a SN has been observed incidentally,

information can be gained on its optical and UV emission. Deep HST images can

be used to find light echoes of SNe, as well as recover SNe interacting with

circumstellar material at very late times. A direct search for the progenitor

stars of SNe can be made in pre-existing HST images of their locations; as the

number of archival HST images steadily increases, along with the number of

newly discovered SNe, positive identifications become progressively more

likely. In Cycle 16, we plan to extend our successful work from previous

cycles. This proposal is complementary to our Cycle 16 survey proposal, whose

primary purpose is to obtain late-time photometry of SNe. It is also

complementary to our Cycle 16 ToO proposal, which is designed to pinpoint the

locations of recent SNe to help determine their progenitor stars.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11249

Title:                           Dust Enhancement of the Lyman Alpha Equivalent Width at z ~ 4.5 in the CDF-S

PI:                               Steven Finkelstein

PI Institution:             Arizona State University

 

We propose to study high-redshift Lyman alpha emitting galaxies in order to

discover the true nature of their large equivalent widths.  Lyman alpha

galaxies are interesting to study because they are very faint in the continuum

but exhibit a very strong emission line, beyond what is expected from normal

stellar populations.  It has been believed that the large equivalent widths

seen in high-redshift galaxies are intrinsic, and are caused by hot stellar

photospheres from ongoing star formation.  This would indicate that these

objects are young, with a primitive composition.  It would also indicate that

they could be a significant source of reionization photons.  However, there is

an alternative scenario for the cause of this large Lyman alpha EW.  If the

interstellar medium inside one of these galaxies consisted of clumpy dust

clouds in a tenuous ionized medium, then continuum photons would penetrate

deep into these clouds, while the Lyman alpha photons would be resonantly

scattered at the surface.  This would result in a much higher escape fraction

for Lyman alpha photons than for continuum photons, effectively enhancing the

equivalent width.  Thus, a galaxy with this ISM and older stars could be made

to look like a young, star-forming galaxy on the basis of its Lyman alpha EW.

We will use the GOODS CDF-S treasury data set to measure the continuum colors

of Lyman alpha galaxies, and thereby distinguish between these scenarios:        If

large equivalent widths are due to hot photospheres, the continuum should be

blue, while if they are due to dust enhancement, the continuum should be red.

The GOODS CDF-S dataset has a limiting magnitude that is 2 magnitudes deeper

than our ground-based broad-band dataset.  This will reduce the errors on the

broad-band colors by up to 75%.  To find Lyman alpha galaxies in the CDF-S, we

have narrow-band images which will be used for selection of z ~ 4.5 galaxies.

By combining our narrow band images with the high quality GOODS data, we will

be able to study the cause of the Lyman alpha equivalent width in individual

galaxies at high-redshift.

======================================================================

 

Proposal Category: AR

Scientific Category: STAR FORMATION

ID:                               11250

Title:                           Shedding Light on Feedback:       The Interaction of YSO Outflows in L1551

PI:                               Adam Frank

PI Institution:             University of Rochester

 

Energetic outflows are an ubiquitous phenomena associated with young stellar

objects and are believed to exert a strong effect on their parent molecular

clouds.  In most young clusters the density of newly forming stars implies

that parsec scale outflows may sweep over a significant fraction of the

cluster volume and interact with each other. The nature and dynamics of these

interactions in an environmental context has yet to be investigated in detail.

Thus the time is ripe to push forward the construction of detailed ecological

studies of star formation where the cloud, stars and outflows are seen as a

coherent interacting system.  Such a perspective is however hampered by the

complexity of the problem. Proceeding forward will require isolation of key

components of an overarching theory. Finding relatively clean examples of

outflow feedback is critical to exploring more general issues star formation

ecology.  We seek to carry forward a well focused study of outflow feedback in

the L1551 region.  Using Adaptive Mesh Refinement MHD code we propose a

computational study of multiple jets interacting with their environment and

their role in altering the properties of their parent cloud.  The questions to

be addressed are:   What is the combined effect of jets oriented at different

angles on the overall turbulent motions in the cloud; How effective is the

coupling between outflows atndcloud material; How effective are the combined

outflows at disrupting and dispersing the cloud material; How effective are

the combined outflows at seeding turbulence into the cloud.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11251

Title:                           Beyond the Textbook:         Temporal Systematics of Planetary Nebula Evolution

PI:                               Adam Frank

PI Institution:             University of Rochester

 

The study of PN shapes has been propelled forward by the high angular

resolution of HST into a state of flux. Currently the field is undergoing a

profound reassessment as mechanisms such as binary companions, accretion

disks, MHD outflow launching and jets become central to a fundamental

understanding of these objects.  Making progress now requires more systematic

studies of PN databases (such as HST) which show strong evidence that nebular

shapes change dramatically in time. In order to connect PN shapes to

evolutionary mechanisms we propose using high resolution Adaptive Mesh

Refinement MHD codes, built by the PI, to follow the evolution of three broad

classes of models and compare their predictions with the existing data,

particularly a new catalogue of HST PN images.

======================================================================

 

Proposal Category: AR

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11252

Title:                           Ultraluminous X-ray sources in elliptical galaxies and the X-ray binary/globular cluster connection

PI:                               Elena Gallo

PI Institution:             University of California - Santa Barbara

 

We propose to exploit archival HST/ACS observations of 100 spheroidal galaxies

in the Virgo cluster in order to identify the optical counterparts of about

4500 bright X-ray binaries from our ongoing Chandra survey.  Based on the

shape of the cumulative luminosity function scaled to the mass of the whole

sample, we expect to detect around 100 Ultraluminous X-ray Sources (ULXs):    the

combination of the high resolution and sensitivity of the ACS images will

effectively allow us, for the first time, to discriminate between background

sources and genuine ULXs for each and every candidate. This, in turn, will

allow us to determine whether early-type galaxies harbor ULXs in abundance,

and, if so, whether they are preferably in globular clusters, also readily

identifiable from the HST images. In addition, this unprecedented catalog of

optical counterparts of X-ray sources will yield new information on the

properties of low mass X-ray binaries and their association with globular

clusters. Finally, by producing a large and clean sample, our study will

settle the debate on the presence of a break in the X-ray luminosity function

of this population.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11253

Title:                           Sizes and Morphology of z=3.1 Lyman Alpha Emitting Galaxies in the Extended CDF-S

PI:                               Eric Gawiser

PI Institution:             Rutgers the State University of New Jersey

 

Lyman Alpha Emitting galaxies (LAEs) seen at high redshift appear to be

galaxies in the act of formation.  They are currently the most promising

candidates for the progenitors of typical spiral galaxies like the Milky Way.

The LAEs tend to be younger, lower in mass, and less chemically evolved than

the better-studied Lyman Break Galaxies (LBGs).  Wide-field ACS imaging allows

us to study the physical properties of these objects at kpc scales to gain a

better understanding of the interconnected processes of mergers and star

formation that play fundamental roles in galaxy formation.    We will use

archival ACS images of the Extended Chandra Deep Field-South from GEMS, GOODS,

and UDF to study the size and morphology of our sample of 162 Lyman Alpha

Emitters at z=3.1, 47 of which have confirmed spectroscopic redshifts.  We

will perform the identical analysis on a sample of 34 spectroscopically

confirmed Lyman Break Galaxies at 2.7<z<3.9 to compare the physical properties

of these two families of high-redshift galaxies. At this redshift, the ACS

F606W and F850LP bands trace the rest-frame ultraviolet radiation from ongoing

star formation.    We will determine parametric measures of morphology (Sersic

radii, CAS parameters, Gini coefficient, M20) along with non-parametric

measures (half-light radii, number of star-forming clumps, size and separation

of clumps) to provide critical constraints upon models of galaxy formation.

We will use the objects that lie in the deeper GOODS and UDF regions to model

uncertainties in the GEMS results.  We will correct the astrometric zeropoints

of the GEMS images and reproject them to match the standard GOODS/MUSYC

pixelization scheme for this field and will offer these images to the

community via the HST archive.

======================================================================

 

Proposal Category: AR

Scientific Category: COOL STARS

ID:                               11254

Title:                           Analysis of Red Giant Oscillations from a 27 Day ACS/WFC Time-Series on NGC 6397

PI:                               Ronald Gilliland

PI Institution:             Space Telescope Science Institute

 

Observations of solar-like oscillations have started to provide excellent

results with firm detections in recent years for dwarfs, subgiants and red

giant stars -- all with radial velocities.  We are now poised to further

exploit these recent successes with more systematic exploration of

oscillations in stars across the color-magnitude  diagram (CMD).   Giants are

of particular interest as allowing tests of stellar structure and evolution in

this complicated time in a stars life, while presenting observational signals

of much larger amplitude than for dwarfs.  Study of stellar oscillations

requires unusual combinations of long time coverage to  obtain the requisite

frequency resolution, and precision to detect the fraction of a mmag amplitude

modes to be studied here.  Time coverage of one week is a lower limit for

study of modes which in the giants will have periods of 0.25-3 days, while

intensive observations over multiple weeks would be ideal.  We will show

excellent success at detecting oscillations in giants (all of which are

strongly saturated in these data) from a 7 day observation program (GO 9750)

conducted for extrasolar planet detection in the galactic bulge.  This

proposal is for analysis of giants serendipitously observed as part of GO-

10424 a 126 orbit program with ACS/WFC on NGC 6397 to probe the bottom of the

white dwarf cooling sequence. These ~400 exposures over 27 days for NGC 6397

will allow asteroseismic results on ~40 giants, including mode lifetime

estimates not possible at only 7 days.

======================================================================

 

Proposal Category: AR

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11255

Title:                           Simulating the Evolution of the Galaxy Luminosity Function from z=6 to the Present.

PI:                               Fabio Governato

PI Institution:             University of Washington

 

Using hydrodynamical simulations of galaxy formation we will provide (1)

updated predictions for the luminosity function of galaxies in HST and Spitzer

bands from z ~ 6 to the present and (2) study the physical mechanism that

drives its evolution.  Particular emphasis will be on providing results easily

comparable with the real observations:  Using the code Sunrise (developed by

P.Jonsson, UCSC) we will produce artificial images at kpc resolution for

thousand of galaxies to obtain individual magnitudes and light profiles in HST

and Spitzer bands that keep into account the detailed geometry of each galaxy

and a self consistent treatment of dust reprocessing of light sources.   The

simulations will consists of a large, 800 million particles SPH simulation of

a 50 Mpc cosmological volume and of several very high resolution simulations

of individual galaxies in a cosmological context. While the large volume will

provide us with a large statistical sample, the high resolution simulations

will allow us to identify the physical mechanisms (cold flows, energy

feedback, mergers) that drive the evolution of the galaxy Luminosity Function

at different masses and cosmic times.  This double approach will allow us to

properly evaluate any numerical effects present in the simulations.

======================================================================

 

Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11256

Title:                           Neon Abundance in Hot Central Stars of Planetary Nebulae: A New Clue to Late Stellar Evolution

PI:                               James Herald

PI Institution:             The Johns Hopkins University

 

We propose to analyze archival HST spectra of a selected sample of central

stars of planetary nebulae (CSPN) for which FUSE spectra are also available.

The primary goal is to derive the neon abundance in their stellar atmospheres.

While the abundances of most "hydrogen-rich" CSPN are well explained by

evolutionary models, those of "hydrogen-deficient" CSPN are not.  One

explanation for the abundances of the latter is the "born-again" scenario,

which predicts enhancements in carbon, oxygen, and neon resulting from a late

helium shell flash.  From recent modeling of far-UV and UV spectra with a

revised version of the stellar atmosphere code CMFGEN which included high-

ionization stages of neon, we discovered that in very hot (Teff > 80,000 K)

CSPN, several transitions from high ionized neon may be visible at UV and far-

UV wavelengths (Herald, Bianchi & Hillier, 2005).  Our modeling shows that

these features are  highly sensitive to the neon abundance.  We will model

archival HST spectra concurrently with FUSE spectra to determine the stellar

parameters such as effective temperature, and also the neon abundance. Our

sample of hot CSPN spans a range of evolutionary phases.  The neon abundance

is an important clue to the chemical processing and subsequent dredge-up and

mixing in the stellar atmosphere as predicted by the born-again scenario.

Also, neon is a key component to understanding how CSPN contribute to the

chemical enrichment of the surrounding ISM.  This study will probe the late

stages of stellar evolution with unprecedented diagnostics.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11257

Title:                           Dust lanes since z~1

PI:                               Benne Holwerda

PI Institution:             Space Telescope Science Institute

 

Dust lanes are an iconic part of edge-on spirals which predominantly occur in

the larger faster-rotating disks (V > 120 km/s). This observational fact has

now been well established and linked to the vertical gravitational stability

of spiral disks:          the ISM in the massive disks collapses into the thin lanes.

A survey of distant (z<1) edge-on spirals in the Extended Groth Strip will

give the corresponding critical velocity at which dust lanes appear and the

fraction of spirals that display them. This will allow us to study the

evolution in dust disks with redshift.  This survey will have implications for

the number of massive HI-rich disks, the balance between ISM and SFR in

earlier disks and the Tully-Fisher relation.

======================================================================

 

Proposal Category: AR

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11258

Title:                           Removing the herring-bone pattern-noise from *all* STIS Side-2 CCD data:         a factor ~3 enhancement in sensitivity

PI:                               Rolf Jansen

PI Institution:             Arizona State University

 

When STIS resumed operations in July 2001 using the redundant "Side-2"

electronics, the read-noise of the CCD detector appeared to have increased by

~1 e- due to a superimposed and highly variable "herring-bone" pattern-noise.

For the majority of programs aiming to detect signals near the STIS design

limits, the impact of this noise is far more serious than implied by a mere 1

e- increase in the amplitude of the read-noise, as it is of a systematic

nature.     We have perfected a method to cleanly remove this pattern-noise

from raw STIS CCD frames. It is robust, but too costly in terms of CPU time

and overhead to incorporate into the regular HST/STIS OTFR-pipeline.

Systematic application therefore demands a one-time dedicated off-line effort

beyond the scope of the work outlined in the STIS close-out calibration plan.

As a service to the STIS user community, we propose to fully remove this

excess noise from *all* raw, un-binned, "Side-2" STIS/CCD frames, and so

significantly augment the potential of the STIS data base for future NUV--NIR

archival research. The noise characteristics and effective sensitivity of the

resulting cleaned data, to be delivered back to the HST Archive, will closely

match those of CCD data taken during operations with the primary electronics -

-- representing a gain of a factor ~3 in sensitivity at faint flux levels, at

low surface-brightness levels, as well as at small spatial scales. All

software will be documented and made available to the community.     This

archival calibration legacy program requests a modest, but necessary,

investment of resources to assure a long-lasting STIS legacy. Science programs

that will benefit include:      (1) *all* STIS/CCD spectroscopy of faint point- or

extended sources; (2) *all* STIS/CCD imaging of faint point sources or low

surface-brightness extended sources; and (3) *all* STIS/CCD programs that

combine data obtained with both primary and redundant electronics.

======================================================================

 

Proposal Category: AR

Scientific Category: SOLAR SYSTEM

ID:                               11259

Title:                           Comprehensive Analysis of Neptune's Features

PI:                               Erich Karkoschka

PI Institution:             University of Arizona

 

Hubble took an amazing data set of Neptune in nine GO programs between 1994

and 2006, consisting of 408 WFPC2 exposures with several filters present in

each program.  The PIs of these programs, Hammel, Sromovsky, and Rages,

published a variety of results about Neptune's atmosphere based on each

program.  However, the typical size of the grants for each program did not

allow all scientific questions of these rich data sets to be addressed. I

propose to analyze these 400 images to create a consistent data set spanning

12 years, and I will make even the intermediate results available, such as 400

consistently calibrated images.  The combined data set will then be able to

address more far reaching questions than could be done by single data sets.

Whereas previous studies focused on only a few center-to-limb measurements for

a limited selection of latitudes and wavelengths, I will investigate the whole

data set and analyze 16,000 center-to-limb curves.  I will use the principal

component analysis and various statistical tests to find the hidden variations

on Neptune.  I created software for a similar project on Hubble's Saturn

images.  I am ready to adapt and apply it to Hubble's Neptune images. The huge

number of variable features on Neptune contain an ideal probe about

atmospheric dynamics.  Previous investigations have only scratched pieces of

the surface of this treasure.  It is time for a comprehensive study of the

whole data to discover fundamenatal insights about atmospheric dynamics.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11260

Title:                           Galaxy Shapes and Gravitational Lensing

PI:                               Charles Keeton

PI Institution:             Rutgers the State University of New Jersey

 

The mass distributions in gravitational lens galaxies--even just the stellar

components--are almost certainly more complicated that we usually assume.

This probably contributes to the problems with lensing constraints on the

Hubble constant.  It might also confound studies of dark matter substructure:

we recently found that edge-on disk components in elliptical lens galaxies can

create "anomalous" flux ratios similar to those often attributed to dark

matter substructure.  We propose to critically examine how galaxy shapes

affect these applications of gravitational lensing.  We will use real galaxies

from the GEMS (Galaxy Evolution from Morphology and SEDs) survey to construct

a large catalog of mock lenses.  Working with mock lenses allows us to perform

controlled experiments; but the power comes from using real galaxies so that

we automatically include structures that are more general than conventional

parametric lens models yet are guaranteed to be realistic.  We will use the

catalog of mock lenses to determine whether the observed incidence of

anomalous flux ratios can be explained by "disky" lens galaxies or requires

dark matter substructure.  In doing so, we will derive new constraints on the

amount of dark matter substructure required or allowed by gravitational

lensing, which realistically account for the complexity in galaxy (stellar)

mass distributions.  We will also use the mock lenses to provide the first

objective calibration of non-parametric lens models.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM IN EXTERNAL GALAXIES

ID:                               11261

Title:                           Dynamically-Driven Star Formation in M51

PI:                               Jin Koda

PI Institution:             California Institute of Technology

 

We propose to investigate gas dynamical environments around star forming

regions in the ground-design spiral galaxy M51. The archival HST/ACS Halpha

image will reveal the location and properties (e.g. size, luminosity) of HII

regions. The CARMA key project observes molecular gas over the entire M51

disk, overlaying the gas density and velocity structures on the HII image.

CARMA has sufficient spatial and velocity resolutions for revealing dynamical

environments (e.g. shocks, shears) around individual star forming regions. We

will correlate the HII region properties with their dynamical environments.

The comparison of CARMA and HST image will reveal the previously unseen

connection between galactic gas dynamics and the trigger of star formation.

======================================================================

 

Proposal Category: AR

Scientific Category: COSMOLOGY

ID:                               11262

Title:                           Deepening the Hubble UDF - Constraining the High-z Galaxy Luminosity Function Faint End Slope and Reionization

PI:                               Anton Koekemoer

PI Institution:             Space Telescope Science Institute

 

We propose to significantly improve the depth of the Hubble Ultra Deep Field

(UDF) by ~0.4-0.5 magnitudes (equivalent to doubling the exposure time of the

original UDF), through recalibrating and reprocessing the original UDF ACS

data with improved reference files and new techniques to remove a variety of

electronic instrumental signatures from the images. Since ACS has now been in

operation for almost 5 years, this provides an opportunity to improve

significantly upon the original calibration which had been performed using the

best available information 18 months after the installation of ACS. Our team

has the demonstrated expertise to carry out this recalibration and

reprocessing, and we also have the demonstrated ability to release such

products to the commmunity on a timely basis. We propose this as an Archival

Legacy program because the resulting dataset, as well as the techniques that

we are using, will be of great value to the community and should enable

significant new science to be obtained from this unique dataset. In addition,

the resulting improvements on the number counts of redshift ~6 dropout sources

will significantly improve the current uncertainties in this field regarding

the faint end slope and normalization of the luminosity function of the

redshift ~6 population, and ultimately the role played by these sources in

reionizing the universe.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11263

Title:                           Modeling Coronagraphic Images of Beta Pictoris and other Debris Disks with Gas

PI:                               Marc Kuchner

PI Institution:             NASA Goddard Space Flight Center

 

We propose to study the dynamics of dust grains in the Beta Pictoris disk and

to model the X pattern, otherwise known as the "warp," revealed in ACS

Coronagraph images.  We will use our models to test the idea that the X

pattern does not stem from the gravitational perturbations of a planet and we

will tie together what we know about the dust and what we know about the gas

in this nascent planetary system.  We will provide numerical tools to the

astronomical community that they can use to model other new and upcoming HST

images of debris disks with gas.

======================================================================

 

Proposal Category: AR

Scientific Category: UNRESOLVED STELLAR POPULATIONS

ID:                               11264

Title:                           Blue Tilts and Other Properties of Halo Globular Clusters in Nearby Galaxies - Cosmological or Observational Bias?

PI:                               Arunav Kundu

PI Institution:             Michigan State University

 

Old metal-poor globular clusters are seen in large numbers in the halos of all

nearby galaxies. Cosmological simulations suggest that these clusters, which

appear as the blue peak in the typical bimodal color distribution of globular

cluster systems, are among the first objects to form at high redshift.  Until

recently these primordial clusters were assumed to be `universal' because the

properties of blue globular clusters found in all types and sizes of galaxies

appeared to be identical. A series of new ACS-based studies, using the ACS

Virgo Cluster Survey (GO-9401) data and other samples (GO-9427, GO/DD-9714),

suggest that there is a mass-metallicity relation in the blue halo globular

clusters. The brighter blue clusters trend to redder colors in this `blue-

tilt' phenomenon. This seems to suggest that larger globular clusters have

self enriched either because they were formed in large gas clouds, or because

in the past they had significant dark matter halos that have subsequently been

stripped. These ACS studies also find that the mean metallicity of the halo

clusters increases with the mean mass of the host galaxy. It has been argued

that this is evidence of self enrichment in large halos and points towards an

in situ model of galaxy formation. We suggest that both these correlations are

caused by subtle systematic observational effects that have been overlooked in

previous studies. We propose to undertake a systematic analysis of the

globular cluster systems of the 145 galaxies observed by the ACS Virgo and

Fornax cluster surveys (GO-9401, GO-10217), and the mosaic of M104 (GO/DD-

9714) in order to answer the crucial question, `Just how universal are the

properties of the metal-poor halo globular clusters?'. These ACS observations

are likely to remain the largest globular cluster datasets for the foreseeable

future. Our independent analysis of these extended datasets will provide an

important check on the results found for globular cluster systems and their

implications on galaxy formation and evolution.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11265

Title:                           Highly Ionized Plasma in the Milky Way:            A Benchmark for Feedback Studies in the Universe

PI:                               Nicolas Lehner

PI Institution:             University of Notre Dame

 

We propose to produce an homogeneous study of the high-resolution STIS E140H

(1.5-2.7 km/s resolution) spectra of the interstellar Si IV, C IV, and N V

absorption along 26 extended Galactic sight lines to study the properties of

highly ionized gas in the Milky Way.  Absorption from these ñhigh ionsî is

used to probe hot gas from the Milky Way to high-redshift primordial galaxies.

However, only in our own Galaxy have they been observed with high enough

spectral resolution to fully resolve the line profiles. Such observations have

revealed surprisingly narrow absorbing clouds that would not have been

identified at lower resolution and that likely trace non-equilibrium cooling

or photoionization of feedback-driven gas.  The sight lines chosen for study

in this work sample a variety of physical environments or structures (e.g.,

the lower Galactic halo, H I shells and supershells, spiral arm and interarm

gas, and evolved supernova remnants).  The very high resolution of the

observations to be analyzed will allow us to derive properties for the

individual physical clouds connected to such structures and to study effects

unobservable at lower resolutions where the clouds are smeared together. Our

survey has three main goals:        1) to produce an homogeneous reduction and

analysis of the archival E140H spectra of these stars; 2) to determine the

primary ionization mechanisms responsible for the highly ionized gas in

various physical environments in the Milky Way; 3) to understand the physical

origins of the different types of highly-ionized gas so that the signatures

seen in the Milky Way might be used for understanding highly ionized gas in

the halos of neighboring galaxies, in starburst outflows, and in primordial

galaxies.

======================================================================

 

Proposal Category: AR

Scientific Category: STAR FORMATION

ID:                               11266

Title:                           Radiation-induced Grain Dynamics in Dust Disks:       Radiation Pressure, Poynting-Robertson Drag, and Photophoresis

PI:                               Aigen Li

PI Institution:             University of Missouri - Columbia

 

We propose a theoretical program to rigorously calculate the radiation

pressure and Poynting-Robertson drag parameters for both porous and compact

grains in dust disks illuminated by stars of a wide range of spectral types,

using the scattering parameters obtained from our HST Cycle 15 theory project.

We also propose to study the rotational excitation of grains in gas-rich,

optically thin disks (through collisions with neutrals, ions, "plasma drag"

which may drive them to rotate suprathermally) to test the "photophoresis"

hypothesis which was recently invoked to explain the central clearing and the

formation of narrow rings in dust disks. This program will create a web-based

library of radiation pressure and Poynting-Robertson drag parameters for both

porous dust and compact dust (including nano-sized grains) as a function of

size, composition, porosity (for porous dust), and stellar spectral type. This

library will be made publicly available via the WWW at

http://www.missouri.edu/~lia/. These parameters are essential (1) for modeling

disk dynamics to interpret the un-smooth structures (e.g. asymmetry, warps,

inner holes, clumps, rings) seen in scattered light images of disks obtained

with HST, and (2) for reliably determining the dust removal and replenishment

rates of debris disks as well as disk evolution.

======================================================================

 

Proposal Category: AR

Scientific Category: STAR FORMATION

ID:                               11267

Title:                           Dynamical Heat Re-Distribution Modeling in Hot-Juipter's

PI:                               Douglas Lin

PI Institution:             University of California - Santa Cruz

 

Observations of transiting hot-Jupiter's have opened a new avenue for

exploring the structure and atmospheres of giant extra-solar planets.

Significantly different then our own giant planets, tidally locked hot-

Jupiter's are subject to intense irradiation from their host star, which

drives supersonic winds across the face. In this proposal we describe a study

coupling full 3-dimensional radiative hydrodynamic models to radiative

transfer models and detailed opacity studies. Noticeably absent in current

studies, these models will allow us to self-consistently explore existing

observations and predict properties of new objects, including spectral

signatures and light curves. These predications should be directly testable by

the Hubble Space Telescope and should lead to a greatly improved understanding

of atmospheric physics on the surface of extra-solar planets.

======================================================================

 

Proposal Category: AR

Scientific Category: QUASAR ABSORPTION LINES AND IGM

ID:                               11268

Title:                           New Synthesis Models of the Extragalactic Ionizing Background

PI:                               Piero Madau

PI Institution:             University of California - Santa Cruz

 

The intergalactic medium (IGM) contains evidence of the epochs of galaxy

formation, metal enrichment, reionization, and reheating of the baryons left

over from the Big Bang. Hydrogen, helium, and many heavy elements (C, Si, N,

0) observed by Hubble through quasar absorption line studies are kept highly

ionized by the extragalactic UV/soft X-ray background (UVB) from active nuclei

and star-forming galaxies. The spectrum and intensity of the UVB is one of the

most uncertain yet critically important astrophysical input parameters into

cosmological simulations of the IGM. It provides the ionization corrections

needed for interpreting QSO absorption-line data and derive crucial

information on the distribution of primordial baryons and of the

nucleosynthetic products of star formation. We propose here to build improved

synthesis models of the UVB intensity, spectrum, and evolution with redshift

using the radiative transfer code CUBA, updating and extending our previous

results (Haardt & Madau 1996). We will adopt up-to-date determinations of the

quasar optical/X-ray luminosity functions and intrinsic spectra, intergalactic

photoelectric absorption, and cosmic star formation history from GOODS/ACS

data. This research will make use, enhance the value of and have a lasting

benefit for past and observational programs with the HST. We will make the

latest version of CUBA freely available for public use, allowing for several

user-supplied quantities such as source emissivity  as a function of frequency

and redshift, and amount of intervening absorption.

======================================================================

 

Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11269

Title:                           Determining O star mass loss rates from Sulfur wind lines.

PI:                               Derck Massa

PI Institution:             SGT, Inc.

 

The winds of massive stars power and enrich the ISM, control the evolution of

the stars, determine their ultimate fate and the nature of their remnants,

determine the appearance of HRDs in young, massive clusters and star-bursts,

and play a major role in the initial stages of massive star cluster formation

and evolution.  Thus, recent suggestions that O star mass loss rates are up to

ten times less than previous observational determinations or theoretical

expectations warrant further investigation.  Perhaps the most compelling

evidence for reduced mass loss rates comes from analyses of the far UV P V

1118, 1128A resonance doublet, which has become widely accessible since the

launch of FUSE.  Because Phosphorus has a low cosmic abundance, this doublet

never saturates, providing accurate estimates of the mass loss rate times the

ionization fraction.  By examining the strength of this doublet as a function

of temperature for a large sample of stars, it is argued that the ion fraction

of P V must be near unity somewhere in the O star range.  If this conjecture

is correct, then the mass loss rates inferred from P V never exceed 10-15% of

previous expectations.    In this proposal, we intend to verify this important

result by analyzing HST and FUSE data for the wind lines of three adjoining

stages of Sulfur (S IV, V and VI) in a sample of LMC O stars. We show how the

analysis of these lines can furnish a direct measurement of the mass loss rate

from UV wind lines alone, without the need to assume an ion fraction.  As a

result, they provide a powerful verification of the P V results.  Furthermore,

we argue that our results should not be strongly affected by clumping in the

winds, a mechanism often invoked to explain the differences between different

observational measures of mass loss rates.

======================================================================

 

Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11270

Title:                           The Effective Temperatures and Physical Properties of O- type Stars at Low Metallicity

PI:                               Philip Massey

PI Institution:             Lowell Observatory

 

An accurate knowledge of the effective temperatures of O-type stars is the key

to knowing their other physical properties.  Improvements in stellar

atmosphere models in the past few years have significantly reduced the deduced

temperatures of Galactic O-type stars due to the effects of wind- and line-

blanketing.  At the lower metallicities of the SMC and LMC, blanketing should

have a lesser effect, but there is considerable disagreement in the literature

at present as to the effective temperatures scale for SMC and LMC O stars.  We

plan a comprehensive study using HST archive UV data supplemented by optical

ground-based data recently obtained with the Magellan 6.5-m telescope.  In

addition to using improved data, our study will apply different models

(FASTWIND and CMFGEN) to the same data-sets, and we will also separately and

jointly determine physical parameters based upon the UV and optical spectra.

This will lead to a much better understanding of where  the any systematic

differences originate.  In the end, we expect to have not only a definitive

effective temperature scale of low-metallicity O-type stars, but also a very

realistic estimate of what the uncertainties are in that scale.  This study

will also serve as the impetus for long-term improvement in the stellar

atmosphere models of hot luminous stars.

======================================================================

 

Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11271

Title:                           Establishing a Zero Motion Reference Frame for the FGS

PI:                               Bernard McNamara

PI Institution:             New Mexico State University

 

We propose to measure the internal proper motions of the stars in M35 that are

used to calibrate the HST/FGS. The goal of this effort is to remove the

influence these stars have the FGS distortion map. Employing the approximately

108 orbits of available archival FGS data, these motions can be determined to

an accuracy of 0.05 mas/year. By iteratively measuring these motions using

successively longer time bases and then accounting for them in the distortion

map, their influence on this map can be essentially eliminated.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11272

Title:                           An Archival Study of Solar-System-Scale Interstellar Structure

PI:                               David Meyer

PI Institution:             Northwestern University

 

The evidence for significant solar-system-scale (< 100 AU) structure in the

diffuse ISM has increased dramatically over the past decade through multi-

epoch H I 21 cm and optical Na I absorption-line observations of various

extragalactic, pulsar, and stellar sightlines.  Possible explanations for this

structure range from small-scale filamentary geometries to fractal geometries

driven by turbulence to a separate population of small, dense self-gravitating

clouds.  The latest Na I data now indicate that the solar-system-scale Na I

structure is most common in the vicinity of dynamic interstellar regions.

However, the physical interpretation of this structure is unclear because Na I

is not the dominant Na ion in H I clouds.  Such a detailed understanding

requires the diagnostic power of the rich diversity of interstellar species

observable in the UV.  We have identified 13 objects in the HST data archive

with multi-epoch STIS echelle observations of UV interstellar absorption

lines.  We propose to analyze the interstellar lines in the 212 datasets

comprising these observations and probe the physical character of any temporal

profile variations.  Our specific goals in this archival study are to assess

the extent of solar-system-scale structure in the H I gas as well as the

thermal gas pressure, electron density, and dust content of any observed

structure.

======================================================================

 

Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11273

Title:                           Tracing the wind interface of the massive binary Eta Carinae

PI:                               Krister Nielsen

PI Institution:             Catholic University of America

 

The binarity of Eta Carinae has been debated for a long time, but most recent

evidence favors a binary star interpretation. However, very little is known

about the nature of the companion star. Over Eta Carinae's spectroscopic

period many observable wind lines in the NUV/Optical region, have been shown

to exhibit peculiar line profiles with unusual velocity shifts relative to the

system velocity. Some of the lines are exclusively blue-shifted over the

entire 5.54 yr cycle and  their ionization/excitation imply formation in the

interface between the two massive stars. Especially, the He I emission lines

are mainly formed in the wind interface region. Since the wind momentum is

much larger for the primary star than its companion, the wind interface is

located fairly close to the companion. Consequently, by tracing the He I

emission we can construct a radial velocity curve that will describe the

motion of the companion star and will derive the relation between the masses

of the binary system stars. Furthermore, we will measure velocity and

intensity variations in H I and Fe II to further investigate the

ionization/excitation structure throughout Eta Carinae's wind. The analysis of

the central source of Eta Carinae, due to the closeness of the two stars in

the binary system (30 AU) and the intervening matter in line-of-sight towards

Eta Carinae, is extremely dependent on data obtained with high angular

resolving power. The HST archival data is crucial for the continuance of this

project.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11274

Title:                           A Final Calibration of the Primary WFPC2 Emission-Line Filters Using the Orion Nebula

PI:                               C. O'Dell

PI Institution:             Vanderbilt University

 

Emission-line imaging with the WFPC2 has been dominated by use of the F656N, F

658N, and F502N filters.These filters require on-orbit calibration in order to

convert their signals to absolute energy surface brightness units. This has

previously been done, but there is a question of time variation of their

properties and this will be addressed by special observations of the Orion

Nebula as part of calibration program 11038. This archive program will use the

previously adopted method that uses a well-calibrated long-slit reference

sample to calibrate the data. There is also a mid-lifetime set that will allow

tracking variations with time. I will also determine if a new set of multi-

aperture groundbased data is satisfactory for use as a reference source and if

it is, to determine variations in the calibration constants across the

individual CCD detectors and with better time resolution by using five

additional studies.

======================================================================

 

Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11275

Title:                           The Effect of Metallicity on the Rotation Rates of Massive Stars

PI:                               Laura Penny

PI Institution:             College of Charleston

 

Stellar interior models are critical tools used in all branches of astronomy

from chemical evolution and population synthesis studies to the determination

of evolutionary masses. Until recently the effects of rotation were not

included in these codes. The new models show that rotation induces interior

mixing that produces some drastic external changes for massive stars while

they are still core-hydrogen burning. While the inclusion of rotation was

expected to explain the enhanced surface abundances seen in some stars, the

prediction that massive stars have luminosities that are rotation dependent

was not expected. This last prediction creates a serious scatter in the mass-

luminosity relationship and makes the determination of an evolutionary mass

essentially impossible. These new models must be tested to determine if their

treatment of angular momentum is correct. A straightforward method is to

determine if massive starsÍ rotation rates match those predicted by the new

models. At solar or Galactic metallicity (Z = 0.020), massive stars are

expected to quickly slow their rotation speeds while on the main sequence

(MS). Stars at lower metallicity (Z) experience reduced mass loss rates and

subsequently retain more of their angular momentum during the MS. The HST

archive at the Multimission Archive at Space Telescope (MAST) contains spectra

of 180 LMC (Z = 0.007) and SMC (Z = 0.004) O-type stars.  This is an extremely

large sample of O-type spectra, all observed with the same instrument. It

contains both cluster and field stars. These stars represent a completely

uniform, unbiased sample for evaluating the predictions from the new stellar

interior models. Projected rotation velocities for all stars will be obtained

through a cross-correlation methodology that we have used successfully in the

past with both IUE and HST/STIS spectra. Comparisons of the rotation rates of

unevolved (close to ZAMS) stars at low Z to those of the same classes at

higher Z will determine if the initial rotation rates of massive stars are

metallicity dependent. Comparisons of the rotation rates of evolved (close to

TAMS) massive stars to the unevolved stars in the same metallicity environment

will determine the extent of angular momentum (and hence mass) loss during the

core hydrogen burning. The proposed survey represents a critical and needed

test of the treatment of angular momentum in the new stellar models and the

accuracy of the models predictions.

======================================================================

 

Proposal Category: AR

Scientific Category: AGN/QUASARS

ID:                               11276

Title:                           Hydrodynamical models of Narrow Line Regions in Seyfert Galaxies

PI:                               Daniel Proga

PI Institution:             University of Nevada - Las Vegas

 

We propose to study large-scale outflows from Seyfert galaxies (SG). We will

explore our hydrodynamical model of flows influenced by the gravitational and

radiation fields of the central part of SG. The model predicts an outflow in

the polar region which is driven by thermal and radiation pressures and is

confined by a very hot ambient gas accreting on to a central black hole.  Our

preliminary calculation shows that this model promises to explain the

kinematics of winds in the Narrow Line Regions of SG.  We will apply the model

to  NGC 1068, NGC 4151, and Mrk 3 where winds were spatially  resolved by HST.

In particular, we will compute, based on our  wind model, synthetic images and

position-dependent line profiles  (i.e., for many positions along a given

slit) for direct comparison  with the data from the Space Telescope Imaging

Spectrograph.  A similar model can be apply to outflows from other Active

Galactic Nuclei and accreting systems.

======================================================================

 

Proposal Category: AR

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11277

Title:                           RR Lyrae Variables in Local Group Galaxies

PI:                               Ata Sarajedini

PI Institution:             University of Florida

 

We propose to reduce and analyze WFPC2 images of 5 Local Group galaxies in

order to identify and characterize their RR Lyrae variables. These galaxies,

which include NGC 147, IC 10, LGS 3, Tucana,  and Andromeda V, have no

published variability studies using HST imaging.The presence of RR Lyrae

variables would suggest that an old (Age >~ 10 Gyr) stellar population is

present in these galaxies. In  additon, because the minimum-light color of ab-

type RR Lyraes is a constant irrespective of metallicity or period, these

stars can be used to study the extinction properties of each galaxy.

Furthermore, the  period of ab-type RR Lyraes is directly related to their

metal abundance so that we can also study the  metallicity distribution

function of each galaxy. Lastly, it is well known that RR Lyraes are excellent

distance indicators allowing us to measure the distance of each galaxy.

======================================================================

 

Proposal Category: AR

Scientific Category: AGN/QUASARS

ID:                               11278

Title:                           AGN Variability in the GOODS Fields

PI:                               Vicki Sarajedini

PI Institution:             University of Florida

 

Variability is a proven method to identify intrinsically faint active nuclei

in galaxies found in deep HST surveys.  We propose to extend our short-term

variability study of the GOODS fields to include the more recent epochs

obtained via supernovae searchers, increasing the overall time baseline from 6

months to ~2.5 years.  Based on typical AGN lightcurves, we expect to detect

~70% more AGN by including these more recent epochs.  Variable-detected AGN

samples complement current X-ray and mid-IR surveys for AGN by providing

unambigous evidence of nuclear activity.  Additionallty, a significant number

of  variable nuclei are not associated with X-ray or mid-IR sources and would

thus go undetected.  With the increased time baseline, we will be able to

construct the structure function (variability amplitude vs. time) for low-

luminosity AGN to z~1.  The inclusion of the longer time interval will allow

for better descrimination among the various models describing the nature of

AGN variability.  The variability survey will be compared against

spectroscopically selected AGN from the Team Keck Redshift Survey of the

GOODS-N and the upcoming Flamingos-II NIR survey of the GOODS-S.  The high-

resolution ACS images will be used to separate the AGN from the host galaxy

light and study the morphology, size and environment of the host galaxy.

These studies will address questions concerning the nature of low-luminosity

AGN evolution and variability at z~1.

======================================================================

 

Proposal Category: AR

Scientific Category: ISM AND CIRCUMSTELLAR MATTER

ID:                               11279

Title:                           A Legacy Archive PSF Library And Circumstellar Environments (LAPLACE) Investigation

PI:                               Glenn Schneider

PI Institution:             University of Arizona

 

NICMOS coronagraphy, with well-matched template Point Spread Function (PSF)

subtraction, probes the closest environments of occulted targets with the

highest imaging sensitivity in intrinsically high contrast fields at the

smallest radial distances afforded, uniquely, by HST. NICMOS PSF-subtracted

coronagraphy has been invoked in a wide variety of HST programs with science

themes as divergent as detecting and characterizing disks of circumstellar

material in neo-natal stellar environments, to studying faint nebulosity

associated with luminous active galaxies, to searching for planetary-mass

companions in extrasolar planetary systems recently born and in the "stellar

graveyard." The investment in HST time in the execution of these and other

programs, which has resulted in more than 8450 NICMOS coronagraphic images to

date, has met with mixed returns. Stunning (but infrequent) successes,

importantly advancing their fields highlight much more frequent, unfortunately

common, failures arising from highly compromised technically-achievable

performance due to the lack of suitable template PSFs required to produce

high-fidelity, photometrically robust, high contrast coronagraphic images. We

propose to remedy this situation by undertaking a rigorous, homogeneous, and

complete recalibration and analysis of the full archival set of raw NICMOS

coronagraphic images previously obtained and residing in the MAST to create a

Legacy library of template PSFs enabling the recovery of the large body of

science otherwise lost. This PSF library, along with generically applicable

analysis software that we will deliver to STScI, will:     (1) critically augment

the needs of future observational programs reliant on high-fidelity PSF

subtractions, (2) increase their yields and photometric efficacy, (3) reduce

the observing time (HST orbit allocations) otherwise required for near-

contemporaneous reference PSF observations, and (4) greatly enrich the yet-

unrealized potential of the many NICMOS coronagraphic observations already

acquired from the broad spectrum of science programs previously executed. We

will then use the enabling power of the PSF library to re-reduce and re-

analyze all archival NICMOS coronagraphic observations of circumstellar disk

and VLM stellar, brown dwarf, and EJP companion candidate stars (~ 400

targets) to probe for previously undetected circumstellar disks. Through image

analysis and modeling we will ascertain the physical properties of newly-

discovered disks and their constituent grains. With a very large and

homogeneously contrast-limited sample of optimally PSF-subtracted images, we

will also set spatially resolved dust-scattered light flux density limits from

non-detections to constrain the properties of the many IR-excess (and other)

sources in this sample.

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Proposal Category: AR

Scientific Category: HOT STARS

ID:                               11280

Title:                           The Variable Magnetic White Dwarf in the Hyades Eclipsing Binary V471 Tauri

PI:                               Edward Sion

PI Institution:             Villanova University

 

V471 Tau is a detached eclipsing binary in the Hyades cluster consisting of a

hot magnetic white dwarf and a rapidly rotating  K dwarf companion. With an

orbital period of only 12.5 hour, the stellar components emerged from common

envelope interactions which drastically reduced their initially wide

separations. It is the prototypical pre-cataclysmic binary. The white dwarf

exhibits soft X-ray, EUV and optical variations on its 9.25 minutes rotation

period. These variations are due to heavy elements accreted onto the WD's

magnetic poles from the companion's wind. The implied accretion rate from the

companion's wind, however, is so low that a magnetic propeller mechanism must

be rejecting most of the material that attempts to accrete.   We propose a

comprehensive analysis of all existing HST STIS echelle spectroscopic

observations that will focus on:     (1) the variation of line strengths of

accreted ions in the WD photosphere over the 9.25 minute rotation period of

the WD, covering the four years over which STIS echelle spectra were taken;

(2) probe the Zeeman splitting we first detected in a greater mix of metallic

absorptions species, thus accurately determining the magnetic field strength

and its variation at the rotational period; (3) determine the chemical

abundances of accreted metals and study the process of magnetic accretion

onto, and diffusion of heavy elements out of, the photosphere of the magnetic

white dwarf using newly available models and diffusion parameters by Co-I J.

Dupuis; (4) refine the mass of the WD and other system parameters with a more

complete radial velocity curve.

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Proposal Category: AR

Scientific Category: RESOLVED STELLAR POPULATIONS

ID:                               11281

Title:                           The Durations of Starbursts in Blue Compact Galaxies

PI:                               Evan Skillman

PI Institution:             University of Minnesota - Twin Cities

 

The starburst phenomenon is a very important phase of galaxy evolution, and

especially so for dwarf galaxies.  The duration of the burst is important

because it impacts both the evolution of the galaxy itself and the evolution

of the local environment external to the galaxy.  In addition to the physical

conditions and evolution of the galaxy, the length of the burst and degree of

"burstiness" affects the detectability of low luminosity galaxies.  There is

no consensus in the literature on the typical duration of a burst in a dwarf

galaxy; some studies favor durations of roughly 5 Myr, and others roughly 100

Myr.  We propose to resolve this discrepancy.  The HST archive contains high

quality imaging observations of a number of nearby starbursts in dwarf

galaxies (often called Blue Compact Dwarf galaxies or BCDs).  However, these

have been obtained through a number of diverse investigations focusing on a

wide variety of science questions. Here we propose a systematic, uniform

analysis of these nearby BCDs that will produce star formation histories

(SFHs) with a primary goal of determining the duration of the burst.

Specifically, we will:            (1) reduce the photometry in a uniform manner using

programs optimized for HST observations, (2) use two of the most sophisticated

programs available to derive optimal star formation histories from the

resulting color-magnitude diagrams, including modeling of the effects of

differential extinction, and (3) compare these results and conduct Monte Carlo

simulations in order to securely quantify the uncertainties in the derived

star formation rates.  This approach will allow us, for the first time, to

compare the results for a significant sample in a uniform and unbiased way,

and thus, draw unambiguous conclusions regarding the duration of starbursts in

BCDs.

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Proposal Category: AR

Scientific Category: SOLAR SYSTEM

ID:                               11282

Title:     &