Cycle 13 Abstract Catalog
Generated on: Wed Apr 14 10:07:54 EDT 2004
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Proposal Category: GO
Scientific Category: COOL STARS
ID: 10114
Title: Lyman_alpha FUV observations of the Sun in time and
effects on planetary atmospheres
PI: Edward Guinan
PI Institution: Villanova University
The chromospheric H I Ly_alpha 1215.6 feature is the dominant source of short-
wave emission in the Sun and solar-type stars, contributing about 80-90% of
the total FUV flux and 30-60% of the total flux between 1 and 1500 A. Also,
this important chromospheric line is the major cooling channel for cool star
atmospheres. Accurate Ly_alpha fluxes are the only missing element of our
ongoing "Sun in Time" program. This program studies a sample of single G0-5 V
stars with well-known physical properties that serve as proxies for the Sun
(and solar-mass stars) over their main sequence lifetimes. One of the major
goals of the program is the determination of the spectral irradiance of the
early Sun. Our analyses indicate that the strong XUV emissions of the young
Sun have played a crucial role in the developing planetary system. In
particular, the expected strong Ly_alpha line flux may have greatly influenced
the photoionization, photochemical evolution and possible erosion of planetary
atmospheres, as well as played a role in the origin and development of life on
Earth. The "Sun in Time" data can also be applied to investigate the
atmospheric loss of exoplanets around solar-type stars resulting from XUV
heating, which can eventually lead to the evaporation of "hot Jupiters". We
propose to use HST/STIS-MAMA/E140M to determine accurate FUV and Ly-alpha
fluxes and irradiances for 4 representative solar proxies with ages from 130
Myr to 6.7 Gyr. It is only with HST's high-resolution UV spectroscopy (to
correct for ISM absorption) and the small aperture (to eliminate geocoronal
emission) that the stellar Ly-alpha profile can be reliably modeled and its
flux measured. The proposed study is of capital importance in reconstructing
the evolutionary histories of exoplanets already known and additional planets
that missions such as COROT, Kepler, SIM, and Darwin/TPF will discover in the
coming years.
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Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10115
Title: Rotation of Comet Tempel 1
PI: Michael A'Hearn
PI Institution: University of Maryland
We propose to accurately determine the rotational period of comet Tempel 1.
This is crucial for enabling all of the science associated with the Deep
Impact mission. It will also, in combination with ground-based data already
on hand and images to be obtained from Deep Impact, provide the best dataset
ever for investigating whether excited state rotation exists in any comet
other than Halley.
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Proposal Category: GO
Scientific Category: HOT STARS
ID: 10116
Title: Towards an Accurate Calibration of the Galactic Cepheid
P-L Zero Point
PI: Edward Guinan
PI Institution: Villanova University
The young open cluster NGC 7790 is unique and astrophysically important
because it contains three classical Cepheid variables (CF Cas, CE Cas A, and
CE Cas B). If the distance of NGC 7790 were known with certainty, these
Cepheids would define the zero point for the galactic Cepheid Period-
Luminosity (P-L) relationship. By a stroke of good luck, NGC 7790 also
contains a 10th-mag eclipsing binary located near the turnoff of the main-
sequence of the color-magnitude diagram of the cluster. This important
eclipsing binary has been little studied until now and contains two B1IV-V+B3V
stars with an orbital period of P=6.005 days. With HST we propose to secure
the accurate distance and reddening of QX Cas (and thus of the Cepheids) by
using eclipsing binaries as precise standard candles, as we have demonstrated
in our work on the Large Magellanic Cloud. With absolute radii, temperatures,
and luminosities of the stars known from ground-based and HST observations,
the method is essentially geometric and free from many of the uncertainties
that plague other less direct methods. Light and radial velocity curve data
will be combined with the proposed HST/STIS spectrophotometry (1150-8000 A) to
determine the physical properties of the eclipsing binary and thus to secure
an accurate distance and reddening for NGC 7790. The determination of the
stars' temperatures, reddenings and chemical abundances, and therefore the
cluster's distance, with the necessary accuracy can only be accomplished with
HST. According to our previous experience, we expect a resulting distance
determination with an accuracy of about 2-3%. HST/STIS spectrophotometry will
be carried out also for the three Cepheids to determine their properties and
individual reddenings. Thus, the proposed HST observations could help
eliminate the current nagging uncertainty of the galactic Cepheid zero point
and provide the key for a firm calibration of the P-L relationship.
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Proposal Category: SNAP
Scientific Category: AGN/QUASARS
ID: 10117
Title: The Co-Evolution of Star Formation and Powerful Radio
Activity in Galaxies
PI: Christopher O'Dea
PI Institution: Space Telescope Science Institute
We will carry out a STIS/NUV-MAMA snapshot imaging survey of the most compact
powerful radio galaxies, the Gigahertz Peaked Spectrum (GPS) sources and
Compact Steep Spectrum (CSS) sources. These objects are as powerful as the
large radio doubles but are much smaller (and younger) and are crucial to our
understanding not only of how radio-loud active galactic nuclei (AGN) form and
evolve, but also what role they play in the evolution of galaxies. A very
direct and robust way to address these issues is by high resolution imaging
of the host galaxies of these sources in the UV. This has never been done
before for a sample of these very compact sources, since previous HST/UV
imaging programs have focussed on the larger radio galaxies. The UV emission
can provide crucial information about any recent star formation that may have
occurred as a result of ongoing accretion, mergers, interactions, or
triggering by the radio source. By comparing the starburst properties of GPS,
CSS, and large scale radio sources, we will be able to constrain the evolution
of massive star formation as a function of the relative age of the radio
source.
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10118
Title: Imaging the Chemical Distribution in Type Ia SN Ejecta
PI: Robert Fesen
PI Institution: Dartmouth College
We know Type Ia supernovae are thermonuclear explosions of CO white dwarfs,
but we don't know the specifics of how the nuclear burning process proceeds
from the core outward once it starts. The thermonuclear instability is thought
to start off as a subsonic, turbulent deflagration or burning wave but then,
at some point, may transition into a blast or detonation wave. In such
"delayed detonation" models, differences between normal and subluminous Type
Ia SNe reflect differences in the amount of burning that has occurred in the
pre-detonation phase. More burning helps to pre-expand the WD before passage
of the detontation wave, which then results in different final element
abundances and internal Fe-rich ejecta structure. Directly imaging the 2-D
chemical distribution of ejecta from a Type Ia SN is actually possible in the
case of the subluminous Type Ia SN 1885, which occurred on the near-side of
M31's central bulge. This 119 year old remnant is visible -- from its core to
its outer edge -- via strong optical/UV Ca and Fe line absorptions.
Remarkably, the SNR appears to still be in a nearly free expansion phase,
meaning that the elemental stratification seen present today accurately
reflects SN Ia explosive nucleosynthesis physics. We propose to obtain ACS
WFC/HRC images of SN 1885 in order to take advantage of this extraordinary
situation: Having a young, nearby Type Ia SN remnant visible in silhouette
against a galaxy-size light table. These unique observations will reveal a SN
Ia's Ca and Fe ejecta distribution, density structure, sphericity, and
ionization state as a function of expansion velocity, thereby confronting
various SN Ia models with detailed ejecta stratification and expansion
velocity maps.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 10119
Title: Solving the Mystery of the Short-Hard Gamma-Ray Bursts
PI: Derek Fox
PI Institution: California Institute of Technology
Seven years after the afterglow detections that revolutionized studies of the
long-soft gamma-ray bursts, not even one afterglow of a short-hard GRB has
been seen, and the nature of these events has become one of the most important
problems in GRB research. The forthcoming Swift satellite will report few-
arcsecond localizations for short-hard bursts in minutes, however, enabling
prompt, deep optical afterglow searches for the first time. Discovery and
observation of the first short-hard optical afterglows will answer most of the
critical questions about these events: What are their distances and energies?
Do they occur in distant galaxies, and if so, in which regions of those
galaxies? Are they the result of collimated or quasi-spherical explosions?
In combination with an extensive rapid-response ground-based campaign, we
propose to make the critical high-sensitivity HST TOO observations that will
allow us to answer these questions. If theorists are correct in attributing
the short-hard bursts to binary neutron star coalescence events, then the
short-hard bursts are signposts to the primary targeted source population for
ground-based gravitational-wave detectors, and short-hard burst studies will
have a vital role to play in guiding their observations.
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Proposal Category: GO
Scientific Category: HOT STARS
ID: 10120
Title: The Formation Histories and Dynamical Roles of X-ray
Binaries in Globular Clusters
PI: Scott Anderson
PI Institution: University of Washington
Close binaries are fundamental to the dynamical stability and evolution of
globular clusters, but large populations have been extremely difficult to
identify. Chandra X-ray images provide a revolutionary resource, revealing a
few to dozens of low-luminosity X-ray sources in every cluster deeply
examined; our own Chandra programs uniformly study these ubiquitous X-ray
sources (close binaries and their progeny) in 11 clusters. However, definitive
understanding of the nature of the various X-ray subpopulations requires the
identification of optical counterparts, and HST is the demonstrated key in
these crowded environments. We thus propose a proven, efficient, and uniform,
HST multicolor imaging program for optical identifications in 6 of our
clusters with Chandra data on-hand, but which lack adequate optical images in
the HST archive. The proposed ACS images will permit statistical
classifications into the various subtypes: CVs, qLMXBs, BY Dra's/RS CVn's (and
MSPs). A unique aspect of our program is that our clusters span a range of
physical properties such as central concentration, cluster size, and mass--
essential ingredients in the formation, evolution, and dynamical roles of
cluster binaries. Exploiting this range of properties, we have identified a
relation that provides the first compelling link between the number of X-ray
sources and the predicted stellar encounter frequency in globular cluster
cores. But further progress in understanding the details implicit in this
relationship (e.g., whether CVs and qLMXBs formed primarily via stellar
encounters, while BY Dra's/RS CVn's are mainly primordial binaries) demands
uniform optical identifications for multiple clusters, spanning the full range
physical properties.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 10121
Title: The Core Dynamics of the Dense Globular Cluster NGC 6752
PI: Charles Bailyn
PI Institution: Yale University
NGC 6752 is one of the best-studied dense globular clusters, and a wide
variety of intriguing and anomalous results have been obtained. We propose
ACS imaging of the core of this cluster. This will increase the accuracy of
our previous internal proper motion measurements by almost an order of
magnitude, providing an unprecedented probe of the central potential. The
data will also greatly increase the radial extent of previous work on the
binary frequency and luminosity function of this cluster. Together, the data
will provide a new level of constraints on the dynamics of a dense globular
cluster.
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Proposal Category: GO
Scientific Category: HOT STARS
ID: 10122
Title: Accretion in the closest binary systems known
PI: Danny Steeghs
PI Institution: Smithsonian Institution Astrophysical Observatory
Recently, three variable stars have been identified as likely accreting binary
systems with ultra-short orbital periods. Optical and X-ray observations have
revealed periodicities of 5-10 minutes, making them the closest binaries known
as well as strong sources of gravitational wave emission. Such short-period
accreting binaries form the cornerstone to our understanding of binary
formation and evolution, in particular of the large double white dwarf
population in our galaxy, a candidate progenitor population for Type Ia
supernovae. We propose to obtain the first UV observations of these objects
using STIS in order to (i) determine the temperature of the primary and the
composition of their donor stars, (ii) correlate the UV variability with other
wavebands and determine if the periods are indeed orbital, (iii) look for
dynamical signatures of direct-impact accretion that is expected to govern the
survival rate of double white dwarfs. These UV observations are essential in
order to unequivocally determine whether these are indeed the most compact
binaries known.
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Proposal Category: GO
Scientific Category: AGN/QUASARS
ID: 10123
Title: Microarcsecond Imaging of a Gravitationally Lensed QSO:
2237+0305
PI: Rachel Webster
PI Institution: University of Melbourne
The microarcsecond scale structure of the central region of the
gravitationally lensed quasar, 2237+0305, can be determined from its
wavelength dependent lightcurve if viewed during a microlensing event. We are
monitoring the QSO from the ground at regular intervals to ascertain the onset
of a microlensing event. STIS spectra will then be taken and compared with the
spectra taken after the event. As the microlensing event occurs, we will
measure wavelength-dependent changes in the continuum, and also the variations
in lines with different ionizations. Thus we will use microlensing to directly
probe the structure of the source QSO on microarcsecond scales -- a factor of
ten smaller than those measured by indirect techniques such as reverberation
mapping. An already approved CHANDRA Cycle 4 GO program will provide
complementary X-ray data, thus greatly increasing the wavelength range over
which we hope to probe the quasar's inner structure.
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10124
Title: Physical Processes in Orion's Veil: A High Resolution UV
Absorption Study of the Line of Sight towards the
Trapezium
PI: Gary Ferland
PI Institution: University of Kentucky
Star formation is governed by a complex interplay among magnetic, thermal,
turbulent and gravitational energies. Of these, magnetic energies are the
most difficult to measure. Yet magnetic energies are crucial to the evolution
of molecular clouds if they are comparable to other energies. Unfortunately,
magnetic field strength measurements are sparse. Moreover, detailed field
strength maps exist in only one region of the ISM, the veil of neutral
material in front of the Orion Nebula. From the Zeeman effect in 21cm HI
absorption lines, we have accurate maps of the line-of-sight field strength in
two independent velocity components of the veil. Therefore, the veil presents
a unique laboratory for study of magnetic effects in star forming regions. We
have recently combined archival UV absorption line data with photoionization
models to estimate the veil's density, temperature and level of ionization.
On this basis, we infer that magnetic energies far exceed turbulent and
thermal energies in at least one HI velocity component. This component is
magnetically unique. All other data about star forming regions suggest
equipartition between magnetic and turbulent energies. Our analysis of
physical conditions in Orion?s veil suffers from an important limitation.
Existing UV absorption line data have insufficient spectral resolution to
separate the two HI velocity components. Therefore, our models reflect
average conditions in the two components. Yet actual conditions are likely to
be quite different since one component must lie closer to the source of
ionization. We propose to use STIS to obtain high resolution UV spectra of
Theta 1 Ori A. These data will allow us to model the two velocity components
separately. We can then estimate magnetic and other energies in the two
components. We will determine if the apparent magnetic uniqueness of one
component applies to both, and we will estimate the distances of each
component from the ionizing stars. This study will provide the most
comprehensive information obtainable about the role of magnetic effects in a
star forming region.
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Proposal Category: GO
Scientific Category: AGN/QUASARS
ID: 10125
Title: Where is the Wind in 1H0707-495?
PI: Karen Leighly
PI Institution: University of Oklahoma Norman Campus
We propose three observations using HST STIS of the narrow-line Seyfert 1
galaxy 1H 0707-495 to be coordinated with already-approved deep exposures
using FUSE. A previous HST observation of 1H 0707-495 revealed strongly
blueshifted high-ionization lines, suggesting an origin in an outflowing wind.
Detailed photoionization modeling reveals that the wind line fluxes and ratios
are consistent with two solutions: a high-density, high-column solution,
originating close to the central engine, and a low-density, low-column
solution, located much further out. These two locations, interestingly,
correspond to those predicted by two different physical models for winds in
AGNs. We can differentiate between these models by observing emission line
variability on two time scales, and examining relative variability of OVI
obtained by FUSE and CIV and other lines obtained by HST. We will also look
for profile variability, constrain velocity ionization stratification through
a detailed study of the profiles, and investigate metallicity, which has been
suggested to be high in NLS1s. This program, requiring only a modest amount of
time, is expected to make significant contributions to our understanding of
outflows in AGN, and the structure, origin and metallicity of the broad-line
region.
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Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 10126
Title: The 3-D Shape of the SMC: Is It Tidally Distorted?
PI: Edward Olszewski
PI Institution: University of Arizona
We propose to exploit the exceptional spatial resolution of HST to
definitively show whether the SMC is tidally elongated along the line-of-
sight, and therefore the status of the Milky Way's interaction/destruction of
the Magellanic Clouds. We use BVI ACS images of several crowded SMC fields in
the region predicted by models of the orbit and tidal evolution of the
Magellanic Clouds (and by observations of Cepheids) to have a large depth. We
exploit the red clump feature (and the rarer true horizontal branch) to derive
the depth. Specifically, we will observe six fields along the predicted
region of maximum distance gradient of the SMC, along with two ACS fields and
several WFPC2 fields in the archives, to map out the depth of the SMC in this
region. We are searching for substructure, such as a tidal tail, that may be
present. Crowding in this region of the SMC is so severe that this project
cannot be done from the ground.
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Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 10127
Title: IMAGING A PROTOCLUSTER AT z = 3.1: EFFECTS OF ENVIRONMENT
AND EVOLUTION ON GALAXY POPULATIONS IN THE EARLY UNIVERSE
PI: George Miley
PI Institution: Universiteit Leiden
We propose imaging a rich protocluster, 0316-26 at z = 3.13, with 31 confirmed
Lya cluster members. The bright radio galaxy host is identified with the
progenitor of the dominant cluster galaxy. Because its redshift places Lya
into an ACS narrow-band filter, the protocluster provides a unique laboratory
for studying galaxies at a crucial epoch in the evolution of the Universe. We
shall (i) measure and compare sizes, morphologies and colors of galaxies from
populations detected using 4 different selection techniques (Lyman and 4000A
breaks, Lya and [OIII] excesses), (ii) study effects of an overdense
environment by comparing the properties of protocluster galaxies with z~3
field galaxies from GOODS, (iii) study effects of evolution by relating our
data to observations of similar protocluster/cluster targets at redshifts z =
4.1, 2.2, and 1.2, and (iv) constrain the formation of the most massive
cluster galaxies by investigating the spatial distribution, Lya equivalent
widths and other properties within the 5" radio galaxy host. The ultimate aim
is to disentangle the history of structure development and stellar evolution
for rich clusters of galaxies.
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Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 10128
Title: Probing the Formation & Evolution of M31's Outer Disk and
Halo, Part II
PI: Annette Ferguson
PI Institution: Max-Planck-Institut fur Astrophysik
Over the past several years, our group has conducted a large panoramic ground-
based imaging survey of resolved luminous stars in M31 using the INT Wide-
Field Camera. Our now complete survey covers 40 square degrees around M31,
extending to a major axis distance of ~60 kpc. This survey has led to the
discovery of numerous spatial density and/or colour (metallicity?) variations
within the M31 halo and outer disk, and interim results motivated a successful
Cycle 11 HST/ACS program to obtain deep colour-magnitude diagrams for six
regions exhibiting the most prominent stellar substructure known at that
time, including the giant stellar stream and the clump of stars near the
anomolous cluster, G1. The present proposal requests time to augment our
Cycle 11 program with observations of two new features, a very low surface
brightness fragment lying 3 degrees north-east of center and a high surface
brightness spur of emission in the south-western half of the galaxy, which we
have discovered since 2001. Deep colour-magnitude diagrams reaching 2-3
magnitudes below the horizontal branch will be constructed, allowing detailed
characterization of the luminous evolved stellar populations via the red giant
metallicity distribution, the luminous asymptotic giant branch, the horizontal
branch morphology and the red clump, as well as the detection of a main-
sequence that may be present from any younger component. Together the Cycle
11 and 13 pointings target all prominent stellar substructure known to exist
within 60 kpc of M31.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 10129
Title: Resolving Globular Clusters in NGC 1399
PI: Thomas Puzia
PI Institution: Space Telescope Science Institute
We intend to use the ACS/WFC to measure structural parameters (half light
radius, King core radius and concentration parameter) of individual globular
clusters (GCs) in NGC 1399. Very little is known about structural parameters
of globular clusters as a function of radius outside the Local Group. The
proposed observations, arranged in a 3x3 ACS mosaic, will allow us to perform
the first detailed wide-field study of structural parameters of globular
clusters in a giant elliptical galaxy. In particular we will: 1) study the
size-galactocentric distance relation of globular clusters out to ~55 kpc
(~1.6 eff. radius of the GCS) and determine whether the observed differences
in sizes between metal-rich and metal-poor globular cluster in early-type
galaxies are primordial and thereby reflect fundamental differences in
formation, or are due to projection effects; 2) match the GC position observed
with HST/ACS with X-ray binaries identified over the full Chandra field, and
use the above sizes to constrain physical models for X-ray binary formation in
GCs. 3) The wealth of ground-based data available for this system
(photometry+spectroscopy), will allow us to correlate the structural
properties with other GC properties, such as their chemical composition,
luminosity, etc.
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Proposal Category: SNAP
Scientific Category: STELLAR POPULATIONS
ID: 10130
Title: Systemic Proper Motions of the Magellanic Clouds from
Astrometry with ACS: II. Second Epoch Images
PI: Charles Alcock
PI Institution: University of Pennsylvania
We request second epoch observations with ACS of Magellanic Cloud fields
centered on the 40 quasars in the LMC and SMC for which we have first epoch
Cycle 11 data. The new data will determine the systemic proper motion of the
Clouds. An extensive astrometric analysis of the first epoch data shows that
follow-up observations with a two year baseline will allow us to measure the
proper motion of the clouds to within 0.022 mas/year in each of the two
orthogonal directions (assuming that we can image 25 quasars, i.e., with a
realistic Snapshot Program completion rate). The best weighted combination of
all previous measurements has a seven times larger error than what we expect.
We will determine the proper motion of the clouds with 2% accuracy. When
combined with HI data for the Magellanic Stream this will constrain both the
mass distribution in the Galactic Halo and theoretical models for the origin
of the Magellanic Stream. Previous measurements are too crude for such
constraints. Our data will provide by far the most accurate proper motion
measurement for any Milky Way satellite. With the cancellation of SM4, HST is
expected to transition to two-gyroscope guiding in Cycle 14. This guiding mode
has additional jitter that will decrease the accuracy of all HST astrometry.
Moreover, there will be a 10 degree radius hole about the ecliptic poles that
will be unobservable, which regrettably includes the LMC. So this cycle may be
the last realistic opportunity for this fundamental measurement. If no second
epoch data are obtained, the previous investment of 40 snapshot orbits will be
wasted. There will be no other observatory for at least a decade that can make
this measurement.
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Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 10131
Title: Determining the Origin of Virgo's Intracluster Stars
PI: Robin Ciardullo
PI Institution: The Pennsylvania State University
Intracluster stars constitute about 20% of the total stellar population of a
typical galaxy cluster, and their existence provides a vital clue for our
understanding of cluster formation and evolution. However, to exploit their
probative value, we need to know their origins: are they the remnants of
dwarf galaxies, long since destroyed by the cluster potential, or have the
stars been harassed from their parent galaxies at recent epochs? To answer
this question, we propose to use the Wide-Field Channel of ACS to make an I,
(V-I) color-magnitude diagram of Virgo's intracluster stars. From the
position and morphology of the population's red giant branch, we will be able
to determine the metallicity distribution function of the stars, and thereby
determine their likely origin and ejection mechanisms. Only HST with the ACS
has the sensitivity and resolution to perform this fundamental measurement.
This program has two options. Option one uses conventional methods of cluster
photometry and requires 37 orbits of exposure time. Option two involves a
novel analysis technique, which promises to achieve most of the same science
in two-thirds the time (23 orbits). We describe this alternative method of
analysis and demonstrate its use via simulations.
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Proposal Category: SNAP
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID: 10132
Title: UV Confirmation of New Quasar Sightlines Suitable for the
Study of Intergalactic Helium
PI: Scott Anderson
PI Institution: University of Washington
The reionization of intergalactic helium is thought to have occurred between
redshifts of about 3 and 4. The study of HeII Lyman-alpha absorption towards a
half-dozen quasars at 2.72.9 SDSS quasars, but with special emphasis
on extending helium studies to the highest redshift sightlines. Our proposed
approach has already proven successful, and additional sightlines will enable
follow-up observations at higher S/N with STIS to measure the spectrum and
evolution of the ionizing background radiation, the density of intergalactic
baryons, and the epoch of reionization of the IGM.
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Proposal Category: GO
Scientific Category: AGN/QUASARS
ID: 10133
Title: HST / Chandra Monitoring of a Dramatic Flare 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. As of late 2003 its
brightness has increased twenty-fold in the optical band, and continues to
increase sharply; the X-rays show a similarly dramatic outburst. In both bands
HST-1 now greatly exceeds the nucleus in brightness. 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 seven epochs of HST/STIS monitoring during
Cycle 13, as well as seven epochs of Chandra/ACIS observation (5ksec each). We
also include a brief HRC/ACS observations that will be used to gather spectral
information and map the magnetic field structure. This monitoring is
continued into Cycles 14 and 15. 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 observations will allow us to 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.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 10134
Title: The Evolution and Assembly of Galactic Disks: Integrated
studies of mass, stars and gas in the Extended Groth
Strip
PI: Marc Davis
PI Institution: University of California - Berkeley
We propose a 126 orbit total F606W/F814W ACS imaging program to measure the
evolution of galaxy disks from redshift z=1.4 to the present. By combining
HST imaging with existing observations in the Extended Groth Strip, we can for
the first time simultaneously determine the mass in dark matter that underlies
disks, the mass in stars within those disks, and the rate of formation of new
stars from gas in the disks, for samples of >1,000 objects. ACS observations
are critical for this work, both for reliable identifications of disks and for
determining their sizes and inclinations. Combining these with the kinematics
measured from high-resolution Keck DEIMOS spectra will give dynamical masses,
which include dark matter. Stellar masses can be measured separately from
dark matter using ground-based BRIK and Spitzer IRAC GTO data, while cross-
calibrated star formation rates will come from DEEP2 spectra, GALEX, and
Spitzer/MIPS. The field chosen is the only one where all multiwavelength
needed will be available in the near term. This data will show how the
fundamental properties of disks (luminosity, rotation speed, scale length) and
their scaling relations have evolved since z~1, and also will measure the
buildup of stellar disks directly; these avenues will provide fundamental
tests of models of disk formation and evolution.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 10135
Title: Unveiling the Progenitors and Physics of Cosmic
Explosions
PI: Shrinivas Kulkarni
PI Institution: California Institute of Technology
GRBs and XRFs are clearly highly asymmetric explosions and require a long-
lived power source (central engine). In contrast, nearby core-collapse events
are essentially spherical explosions. However, the failure of spherical
neutrino driven collapses has led to the idea that asymmetric energy release
is essential for the explosion. The recent finding of a Type Ic SN in GRB
030329, the association of the low energy event GRB 980425 with SN 1998bw, the
theoretical development discussed above and the rise of collapsar models make
it timely to consider whether all these explosions contain engines. Given the
uncertainties in theoretical modeling it is clear that observations are needed
to guide models. A priori there is little reason to expect connection between
the ultra-relativistic jet that powers the GRB and the explosive
nucleosynthesis of the ~0.5 solar masses of Nickel-56 that powers the
accompanying supernova. We propose a comprehensive program of ACS photometric
searches (and measurements) for SNe associated with GRBs and XRFs. In
concert, we will undertake ground-based spectroscopy to determine velocity
widths, and measure engine parameters from pan-chromatic afterglow
observations. Our goal is to produce a comprehensive database of engine and
SN physical parameters against which theoretical modeling will be guided.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 10136
Title: Post-AGB Stars in the Halo of M81
PI: Howard Bond
PI Institution: Space Telescope Science Institute
Post-asymptotic-giant-branch (PAGB) stars of spectral types A-F are the
brightest members of Population II. We have shown, using ground-based
observations, that PAGB stars have tremendous potential as highly efficient
standard candles and as tracers of halo populations and late stellar
evolution. Our analysis of PAGB stars in archival HST images of M32, based on
the equivalent of one orbit of HST time, precisely reproduces the accepted
distance. We propose to obtain ACS/WFC and WFPC2 images of fields in the
halo of M81, as another test of the PAGB method. We show that 4 orbits of HST
data will produce a distance of comparable accuracy to the much more laborious
Cepheid technique. If successful on M81, we will propose in the next cycle to
measure the distance to Virgo using our method, a distance ladder that has
only two rungs (trigonometric parallaxes of subdwarfs to calibrate PAGB stars
in globular clusters, and then PAGB stars in Virgo).
================================================================================
Proposal Category: SNAP
Scientific Category: GALAXIES
ID: 10137
Title: Cluster Archeology: The Origin of Ultra-compact Dwarf
Galaxies
PI: Michael Drinkwater
PI Institution: University of Queensland
Ultra-compact dwarf (UCD) galaxies are a new type of galaxy we have discovered
in the central regions of the Fornax and Virgo galaxy clusters. Our most
recent observations in the Fornax Cluster show that UCDs outnumber normal
galaxies in the centre of that cluster. Here we propose snapshot imaging of
UCDs in the Fornax and Virgo clusters to test theories of how these
fascinating objects formed. In particular we wish to image Virgo cluster UCDs
for which we have ground-based Keck spectroscopy to test predictions that they
formed more recently than the Fornax UCDs.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 10138
Title: Searching for the Bottom of the Initial Mass Function
PI: Kevin Luhman
PI Institution: Smithsonian Institution Astrophysical Observatory
The minimum mass of the Initial Mass Function (IMF) should be a direct
reflection of the physical processes that dominate in the formation of stars
and brown dwarfs. To date, the IMF has been measured down to 10 M_Jup in a few
young clusters; there is no sign of a low-mass cutoff in the data for these
clusters. We propose to obtain deep images in the SDSS i and z filters (i=26,
z=25) with the ACS/WFC on HST for a 800"x1000" field in the Chamaeleon I star-
forming region (2 Myr, 160 pc). By combining these HST data (0.8, 0.9 um) with
comparably deep broad-band photometry from ground-based telescopes (1.2, 1.6,
2.2 um) and SIRTF (3.6, 4.5, 5.8, 8.0 um), we will measure the mass function
of brown dwarfs down to the mass of Jupiter and thus determine the lowest mass
at which objects can form in isolation in a typical star forming cluster.
================================================================================
Proposal Category: GO
Scientific Category: AGN/QUASARS
ID: 10139
Title: Structure of the Accretion Disk in the NLS1 NGC 4051
PI: Bradley Peterson
PI Institution: Ohio State University
We propose to obtain a UV spectrum of the narrow-line Seyfert 1 (NLS1) galaxy
NGC 4051 on a target-of-opportunity basis when it goes into a faint state for
the purpose of exploring the variable nature of the shape of the ionizing
continuum in this source. Previous simultaneous X-ray and optical monitoring
of this source reveals that at some times the X-rays and the He II 4686
emission line nearly disappear, while the UV/optical continuum and Balmer
lines are weaker, but present and continue to vary. This suggests that there
is a variable cutoff in the shape of the ionizing continuum, and in the faint
state this occurs at low enough energies to affect all the strong UV lines. By
comparing emission-line flux ratios in the low state to those in high states
and with photoionization equibrium calculations, we can identify the cutoff
energy. The cutoff energy may correspond to a transition radius in the
accretion disk, inside of which the source has entered into a low-radiative
efficiency mode.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10140
Title: Identification of a magnetic anomaly at Jupiter from
satellite footprints
PI: Denis Grodent
PI Institution: Universite de Liege
Repeated imaging of Jupiter's aurora has shown that the northern main oval has
a distorted 'kidney bean' shape in the general range of 90-140¼ System III
longitude, which appears unchanged since 1994. While it is more difficult to
observe the conjugate regions in the southern aurora, no corresponding
distortion appears in the south. Recent improved accuracy in locating the
satellite footprint auroral emissions has provided new information about the
geometry of Jupiter's magnetic field in this and other areas. The study of the
magnetic field provides us with insight into the state of matter and the
dynamics deep down Jupiter. There is currently no other way to do this from
orbit. The persistent pattern of the main oval implies a disturbance of the
local magnetic field, and the increased latitudinal separation of the locus of
satellite footprints from each other and from the main oval implies a locally
weaker field strength. It is possible that these phenomena result from a
magnetic anomaly in Jupiter's intrinsic magnetic field, as was proposed by A.
Dessler in the 1970's. There is presently only limited evidence from the
scarcity of auroral footprints observed in this longitude range. We propose to
obtain HST UV images with specific observing geometries of Jupiter to
determine the locations of the auroral footprints of Io, Europa, and Ganymede
in cycle 13 to accurately determine the magnetic field geometry in the
suggested anomaly region, and to either confirm or refute the suggestion of a
local magnetic anomaly.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 10141
Title: UV spectroscopy of the hot bare stellar core H1504+65
PI: Klaus Werner
PI Institution: Universitat Tubingen, Institut fur Astronomie &
Astrophysik
H1504+65 ist the hottest known white dwarf (Teff=200 000 K). It has an
extraordinary surface composition. The photosphere is devoid of hydrogen and
helium. It is mainly composed of carbon and oxygen (by equal parts) and neon
(2%). We obviously see the exposed core of a former red giant. The
evolutionary history of this unique object is unknown. We have identified
magnesium absorption lines in the soft X-ray photospheric (Chandra) spectrum,
which suggests that H1504+65 may be a O-Ne-Mg white dwarf. We will test this
hypothesis by abundance determinations of Mg and Na. If confirmed, then
H1504+65 would be the most compelling case for the existence of single O-Ne-Mg
white dwarfs.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID: 10142
Title: The connection between star-forming galaxies and low-
redshift quasar absorption line systems
PI: Regina Schulte-Ladbeck
PI Institution: University of Pittsburgh
We have positionally matched our database of over 19,000 star-forming galaxies
(SFGs) from the Sloan Digital Sky Survey (SDSS) against the SDSS QSO catalog.
This has allowed us to discover nineteen bright QSOs with redshifts of less
than or about one behind local SFGs. Two of the QSOs were fortuitously already
observed with HST, and show strong Lyman alpha lines at the emission-line
redshifts of the SFGs with which we matched them
================================================================================
Proposal Category: SNAP
Scientific Category: COOL STARS
ID: 10143
Title: Ultracool companions to the nearest L dwarfs
PI: I. Reid
PI Institution: Space Telescope Science Institute
We propose to conduct the most sensitive survey to date for low mass
companions to nearby L dwarfs. We will use NICMOS to image targets drawn from
a volume-complete sample of 70 L dwarfs within 20 parsecs. The combination of
infrared imaging and proximity will allow us to search for T dwarf companions
at separations as small as 1.6 AU. This is crucial, since no ultracool
binaries are currently known with separations exceeding 15 AU. Only 10 dwarfs
in this sample have previous HST observations, primarily at optical
wavelengths. With the increased sensitivity of our survey, we will provide
the most stringent test to date of brown dwarf models which envisage their
formation as ejected stellar embryos. In addition, our observations will be
capable of detecting binaries with mass ratios as low as 0.3, and will
therefore also test the apparent preference for equal-mass ultracool binaries.
Finally, our observations offer the best prospect to date of detecting
companions significantly cooler than the coolest T dwarf currently known.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10144
Title: The Gas Environment of Comet 9P/Tempel 1 During the Deep
Impact Encounter
PI: Paul Feldman
PI Institution: The Johns Hopkins University
We propose a series of observations of the periodic comet 9P/Tempel 1 in
conjunction with NASA's Deep Impact mission. This mission is a spacecraft
that will release a 360 kg impactor into the nucleus of the comet on July 4,
2005. Our primary objective is to study the generation and evolution of the
gaseous coma resulting from this impact. To this end we plan to obtain
ultraviolet spectra with STIS before, during, and following the impact. As a
secondary objective we will obtain wide-band images of the visual outburst
resulting from the impact. We also plan to use the high resolution capability
of the ACS/HRC, in conjunction with the camera on board the spacecraft, two
weeks prior to impact, to determine the spatial orientation of active jets
emanating from the comet's nucleus and to assess the potential hazards of
these jets to the spacecraft.
================================================================================
Proposal Category: GO
Scientific Category: STAR FORMATION
ID: 10145
Title: Physical parameters of the upper atmosphere of the
extrasolar planet HD209458b
PI: Alfred Vidal-Madjar
PI Institution: CNRS, Institute d'Astrophysique de Paris
Every 3.5 days, the transits of the gaseous planet orbiting HD209458 offers
the unique opportunity to investigate the spectral features of an extra-solar
planetary atmosphere. Using HST, we first discovered the extended upper
atmosphere of HD209458b through the detection of a 15% HI absorption. We
concluded that the hydrogen must be escaping the planet with a lower limit of
10^10 g/s (Vidal-Madjar et al. 2003, Nature 422, 143). With additional
observations, we subsequently detected OI and CII in the upper atmosphere
showing that this atmosphere is hydrodynamically escaping (in "blow off",
Vidal-Madjar et al. 2004). Here we propose to further study this upper
atmosphere to better constrain the "blow off" state by directly estimating the
physical conditions and the flow characteristics. In particular we will
determine the temperature and density distribution in the upper atmosphere,
the density at the Roche lobe, the limit between the lower and upper
atmosphere and their ionization states. Comparison between the optical and
near ultraviolet occultation light curves will provide useful information on
the molecular/haze content of the lower atmosphere. The observation of six
HD209458b transits with a single E230M setting will allow the detection of
many lines adressing these issues. The proposed observations will give us for
the first time a detailed probe of the atmosphere of an "evaporating" extra-
solar planet.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 10146
Title: Solving the problem of the White Dwarf Cooling Sequence
End in M4: an efficent approach
PI: Luigi Bedin
PI Institution: Universita di Padova
The end of the white dwarf (WD) cooling sequence (WDCS) has never been
observed, despite the importance that it has in providing an age estimate of
old stellar systems, independent from the standard method of the main sequence
turn off. The best targets for this investigation are the closest stellar
clusters, and, among them, globular clusters are the most interesting ones.
Being the oldest stellar aggregates, they allow to probe the advanced WD
cooling phases, and the independent age estimate coming from the end of their
WDCS has an important cosmological impact. M4 is the best target for this
investigation. Despite huge observational efforts, we still miss the end of
its WDCS. The ACS camera offers a unique opportunity to identify it. Coupled
with already existing observations, we here prove that we can finally reach it
with only 10 HST orbits. This is probably the last opportunity we have for a
large number of years. The data we are requesting here, will also be used to
complete other two programs of great astrophysical impact: the observational
detection of the main sequence hydrogen burning limit, and the measurement of
the geometrical distance of M4.
================================================================================
Proposal Category: GO
Scientific Category: COOL STARS
ID: 10147
Title: Detecting the elusive low mass companion around epsilon
Indi
PI: Michael Endl
PI Institution: University of Texas at Austin
We propose coronagraphic NICMOS observations of the nearby (d = 3.6 pc) K5V
star epsilon Indi (HD 209100) to search for the unknown companion which causes
a low amplitude radial velocity (RV) trend in our 11 years of precise Doppler
measurements. This RV data set places a lower limit of 4.5 AU for the orbital
semimajor axis of this companion. Moreover, the fact that the RV trend is
lacking any sign of curvature over this long time period clearly points
towards a much larger orbital separation. Epsilon Indi also has a T dwarf
(binary) companion at a separation of 1400 AU. However, these brown dwarf
companions are too distant from the primary to induce the observed RV
variation. It is also unlikely that this nearby star has an unknown stellar (M
dwarf) companion. The RV signal is thus most probably caused by a yet unknown
giant planetary or brown dwarf companion at a separation of more than 5 AU.
Because epsilon Indi is so near to the Sun, it constitutes an ideal target for
high contrast imaging with NICMOS in its coronagraphic mode. Indeed, NICMOS
coronagraphy is capable of detecting objects down to 15 Jupiter masses at
separations greater than 2.3 arcseconds (S/N=25) - precisely the separation
and mass range indicated by our Doppler spectroscopy. Only 2 orbits of
HST/NICMOS observations could directly image the coolest and lowest mass
companion ever found around a solar-type star.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10148
Title: The Masses of the Ultraluminous X-Ray Sources
PI: Joel Bregman
PI Institution: University of Michigan
Ultraluminous X-ray sources are non-nuclear sources in normal disk galaxies
that are second only to AGNs in point-source luminosity. These enigmatic
objects are either stellar mass black holes that are super-Eddington emitters,
or sub-Eddington emission from 1E3-1E4 Msolar black holes. We can distinguish
between these models by a direct determination of the mass of the primary,
which requires knowing the spectral type of the secondary, its period, and its
orbital velocity around the black hole. We propose to obtain UV spectra to
determine the spectral type of two ULX secondaries (optical counterparts), to
infer the masses and radii of the secondaries and their suitability for radial
velocity studies. For another ULX secondary, we already obtained a UV
spectrum showing it to be a B0I star, so we propose three additional
observations, which will yield the characteristic orbital velocity, help
constrain the period, and reveal if the primary is a 1E3-1E4 Msolar black
hole, which would produce velocities > 1000 km/sec.
================================================================================
Proposal Category: GO
Scientific Category: AGN/QUASARS
ID: 10149
Title: The Coevolution of Supermassive Black Holes and Galaxies
at z~3
PI: Chien Peng
PI Institution: University of Arizona
The existence of strong correlations between the mass of supermassive black
holes and galaxy bulge properties implies that there is an intimate connection
between their formation and evolution. How do supermassive black holes grow
and how did the correlations come about? Is the growth of supermassive black
holes coeval with the growth of the bulge, and is a bulge necessary for AGN
activity at high z? We propose to use HST NICMOS to image 9 low-luminosity
broad-line AGNs at z~3 in the restframe B-band, identified through the Lyman-
break technique. This sample is unique because the AGN luminosities are
comparable to Seyfert-like nuclei at z~3, and thus are some of the lowest that
have been selected optically. Because of the low total luminosity of the
sample, the hosts are likely to be Lyman-break galaxies, which are believed to
be the progenitor galaxies of the local Hubble sequence. The goal is to
directly detect their host galaxies and to separate the AGN, in order to study
the host galaxy morphology and luminosity. From measurement of the bulge
luminosity and black hole mass (through available spectra), we will study the
black hole-bulge coevolution out to z~3. We will also compare the luminosity
and morphology of these faint AGN hosts with the more luminous and massive
host galaxies found in previous HST studies of quasars.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 10150
Title: NICMOS observations of A1689
PI: Narciso Benitez
PI Institution: Instituto de Astrofisica de Andalucia (IAA)
The potential of galaxy clusters as ``cosmic telescopes'' has been known for a
long time, but practical results in the pre-ACS era have been scarce due to
two main problems: the uncertainty in determining the magnification
distribution of the cluster (the ``optics'' of the instrument) and the
presence of numerous bright cluster galaxies which cover the field of view and
hinder the detection of background galaxies. We have developed techniques to
solve these two problems working with our ACS observations of A1689, the most
powerful lens in the sky, and for the first time we have been able to
determine the "specifications" of a cosmic telescope with a useful level of
precision, thanks to the detection and identification of more than 100
multiple images with reliable redshift information. We propose to observe the
high magnification region in the A1689 field in the F110W band with a 3x3
mosaic of NIC3 pointings; the resulting image will reach a limiting magnitudes
of 29.5, surpassing in depth the UDF NICMOS observations and providing an
unique dataset with multiple scientific returns.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID: 10151
Title: Testing the Warm-Hot Intergalactic Medium Paradigm
PI: J. Howk
PI Institution: University of California - San Diego
Cosmological hydrodynamical simulations predict that ~30%-40% of the low-
redshift baryons reside in a collisionally ionized phase (log T ~ 5 to 7) of
the intergalactic medium (IGM) associated with large-scale, unvirialized
filaments of galaxies. Recent surveys of O VI gas have lent some support to
the presence of this warm-hot intergalactic medium (WHIM), but the results are
significantly limited by uncertainties in the ionization mechanism (photo- vs.
collisionally ionized) and metallicity of the gas. We are pursuing a large
program to test predictions of the WHIM and to improve existing measurements
of the OVI absorbers. The primary goals are (i) to increase the redshift path
for detection of the hottest IGM, previously only accessible through X-ray
absorption studies, using EUV absorption from Ne VIII and Mg X, and (ii) to
constrain the IGM physics using UV absorption from H I Ly-alpha, C III, C IV,
and O VI. Our team has been awarded a FUSE Legacy program to probe the
moderate-redshift WHIM using unique ionization diagnostics in the restframe
EUV waveband, including O V, Ne VIII and Mg X. Here we propose to complement
our FUSE Legacy program with STIS intermediate-resolution echelle-mode
observations of five moderate-redshift (0.45 < z < 0.98) AGNs. The unique
combination of FUSE EUV and STIS UV spectra will allow us (1) to test the
current models of the WHIM by studying the ionization mechanisms responsible
for producing highly-ionized metals in the IGM and determining the frequency
of genuine high-temperature metal absorbers in the low-redshift IGM; (2) to
investigate the relationship between WHIM and large-scale galaxy structures
using galaxy redshift measurements obtained with DEIMOS on Keck and IMACS at
Las Campanas Observatory; and (3) to determine the ionization state and
metallicity of O VI absorbers in order to accurately assess their contribution
to the total baryon budget. Finally, we will make high-level science products
derived from these data freely available to the general astronomical
community.
================================================================================
Proposal Category: SNAP
Scientific Category: COSMOLOGY
ID: 10152
Title: A Snapshot Survey of a Complete Sample of X-ray Luminous
Galaxy Clusters from Redshift 0.3 to 0.7
PI: Megan Donahue
PI Institution: Michigan State University
We propose a public, uniform imaging survey of a well-studied, complete, and
homogeneous sample of X-ray clusters. The sample of 73 clusters spans the
redshift range between 0.3-0.7. The samples spans almost 2 orders of magnitude
of X-ray luminosity, where half of the sample has X-ray luminosities greater
than 10^44 erg/s (0.5-2.0 keV). These snapshots will be used to obtain a fair
census of the the morphology of cluster galaxies in the cores of clusters, to
detect radial and tangential arc candidates, to detect optical jet candidates,
and to provide an approximate estimate of the shear signal of the clusters
themselves, and potentially an assessment of the contribution of large scale
structure to lensing shear.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10153
Title: Multi-wavelength Observations of Symbiotic Stars in
Outburst
PI: Charles Keyes
PI Institution: Space Telescope Science Institute
To investigate the cause and nature of classical symbiotic outbursts, we
initiated a program of multi-wavelength observations of these events. As
evidence is mounting that collimated outflows (jets) may be associated with
symbiotic outbursts, we also investigate conditions needed for jet production
- a question with broad astrophysical relevance. The first target for our
campaign - the 2000-2002 outburst of Z Andromedae - confirmed the utility and
need for coordinated multi-wavelength observations to make progress in
understanding the nature of the outburst mechanisms in symbiotic stars. FUSE
data were the cornerstone of that project (which included data from the VLA,
MERLIN, ground-based spectroscopy and photometry, Chandra, and XMM, but not
HST). Our Z And observations have motivated us to propose a new scenario that
we term the "combination nova" which is triggered by a disk-instability. To
test this new model, we received HST Cycle 12 and FUSE Cycle 4 time (through
approximately 6/2004) to continue the multi-wavelength approach with
observations at several epochs during the outburst of a second target-of-
opportunity (TOO). That TOO has not yet been triggered. We propose here to
continue this TOO observing opportunity into Cycle 13 (to 7/2005). FUSE Cycle
5 observations (to mid-2005) were recently approved. Coordinated XMM and VLA
observations are also approved. The evolution of the UV spectrum throughout
the outburst plays a vital role in distinguishing between the outburst models
currently in contention for describing outburst behavior. Analysis of our
first campaign has shown that HST observations can play a fundamental role in
the multi-wavelength approach. The combination of high-resolution STIS and
FUSE-band emission and absorption features, time-tagged observations, and
continua provide a unique opportunity to probe the structure and ionization
conditions in the outburst material that can not be accomplished with either
ultraviolet region alone.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 10154
Title: Morphology of z ~ 7-10 galaxies viewed through
gravitational telescopes
PI: Roser Pello
PI Institution: Observatoire Midi-Pyrenees
The aim of these observations is to obtain deep z/ACS and H/NICMOS images in
the core of two lensing clusters, A1835 and AC114, where a few z ~ 7-10 galaxy
candidates have been selected from our ultra-deep JHK imaging program with
Isaac/VLT. Spectroscopic observations have allowed to confirm 2 of these
candidates thanks to the detection of faint emission lines identified as Lyman
alpha at z=7.2 and 10. Our HST project is focused on two main goals: (1) the
morphological confirmation of galaxy candidates lying near critical lines,
and (2) the determination of the physical scales involved in star-forming
regions at z ~ 7-10. These goals should have important implications on our
present knowledge of the galaxy formation process in the early Universe.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10155
Title: A Mini-Survey of Interstellar Abundances in the
Magellanic Clouds
PI: Daniel Welty
PI Institution: University of Chicago
Studies of the interstellar medium in the Magellanic Clouds explore somewhat
different environmental conditions from those typically probed in our own
Galactic ISM. Apart from a few studies of individual sightlines, however,
little is known about the abundances and depletions in the ISM of the LMC and
SMC. HST spectra of three SMC stars indicate that Si and Mg (generally
thought to be major dust constituents) are essentially undepleted in the SMC
gas --- even for components with severe depletions of Fe and Ni. Similar
"anomalous" Si depletions have now been seen in cycle 12 STIS spectra of one
LMC star, though "normal" Si depletions are seen toward a second.
Intriguingly, the "anomalous" Si depletions are all found for sightlines which
probe regions where the 2175 A extinction bump is either absent (most of SMC)
or very weak (LMC2). We therefore propose a mini-survey of interstellar
absorption lines toward 13 stars distributed throughout the LMC and SMC ---
which would more than double the number of Magellanic Clouds sightlines with
extensive and accurate interstellar abundance information. A single STIS
E230M setting will include lines from Zn II, Si II, Fe II, Ti II, Cr II, Ni
II, and several trace neutral species --- allowing the abundance/depletion
pattern to be determined at many locations in the two galaxies. The analysis
of these spectra will have significant implications for (1) making models of
interstellar dust grains (which currently rely heavily on silicates); (2)
understanding the relationships between depletions, dust, and H_2 (which may
be somewhat different in the Milky Way, LMC, and SMC); and (3) interpreting
the gas-phase abundances observed for more distant low-metallicity systems,
such as the QSO absorption-line systems (which exhibit some similar
properties).
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10156
Title: Saturn's Auroral Energy Deposition Coordinated with
Cassini UVIS
PI: John Clarke
PI Institution: Boston University
An in-depth study of Saturn's magnetosphere and auroral processes has begun in
Jan. 2004 with coordinated HST STIS images of Saturn's aurora while the
approaching Cassini measures the solar wind. This program is expected to
establish the degree of solar wind control of Saturn's aurora. The beginning
of the Cassini orbiter tour of the Saturn system in July 2004 will offer new
opportunities for collaborative science. The energetics of Saturn's auroral
processes can best be studied via low resolution UV spectra of the emissions
and the auroral "color ratio". The geometry of the initial Cassini orbits
provides the best observing geometry for UVIS measurements of auroral
energetics when it is close to Saturn on the night side. At such times, it
will be possible to have simultaneous observations of Saturn's southern /
dayside aurora with HST STIS and the northern / nightside aurora with Cassini
UVIS. Both the distributions of the auroral emissions and the energy of the
precipitating particles can be measured simultaneously at conjugate points
north and south. This proposal is to conduct one such simultaneous
observation, which will demonstrate the potential for future cycles. We
request 5 HST orbits to observe a large fraction of one complete Saturn
rotation at the same time as Cassini UVIS. The rotational coverage has been
shown to be of central importance in recent STIS images of Saturn's auroral
activity, which is concentrated in an "active sector" connected with the
strongest SKR radio emissions.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10157
Title: Bulges or disks in the centers of late-type spirals?
PI: C. Carollo
PI Institution: Eidgenossiche Technische Hochschule (ETH)
In a simple view of the Hubble sequence, smaller bulges should be rescaled
versions of bigger bulges. Bulges however have been found to change their
structural properties with decreasing luminosity, approaching at the faintest
end a disk-like, exponential light profile. This indicates a complex mass-
dependent bulge formation history. Particularly, the intermediate-to-small
size bulges have been suggested to form due to secular evolution processes
within their host disks. However, the alleged small bulges may even be
'simply' denser inner regions of the disks. Two major ingredients are missing
in order to (a) understand the nature of bulges in the disk-dominated
galaxies, (b) establish whether and which secular evolution processes actually
occur, and (c) in which mass range they are preferentially active: (1) High-
resolution numerical simulations of disk secular evolution, to provide a
quantitative basis for interpreting real data; (2) Observational diagnostics
which can break the degeneracy between very cold, dense disks and relatively
hot bulges, and to compare with the simulations. We are carrying out a large
N-body + SPH simulations campaign to settle the first issue. Stellar
kinematics are the ideal observational diagnostics. We have acquired ground
kinematic data for the medium-sized bulges. However, both the spectroscopic
and the spatial resolution requirements necessary to trace the relative
contributions of cold and hot motions become very stringent at the faint-end
of the bulge sequence: only the HST can provide radially-extended kinematics
for the smallest bulges. We therefore ask for STIS/G750M spectroscopy to
measure internal resolved stellar kinematics for two small bulges selected
from our previous HST imaging program. Even just these two "data-points" in
this unexplored mass-regime will allow significant progress in the
understanding of the origin of the Hubble sequence: Complemented by our
ground-study of the medium-sized bulges, they will allow us to establish
whether the ratio of cold-to-hot motions in bulges in the intermediate-to-
small mass regime depends on the bulge mass, and, by comparing with our
simulations, to constrain the initial conditions and physical parameters that
allow disk secular evolution processes to grow central bulges similar to
those that are observed along the entire Hubble sequence.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 10158
Title: ACS Observations of the Gravitational Lens B1608+656:
Characterizing the Einstein Ring
PI: Christopher Fassnacht
PI Institution: University of California - Davis
We request time to obtain ACS deep images of the B1608+656 gravitational lens
system to fully characterize its enclosing Einstein ring with high signal-to-
noise ratio (SNR). These data will allow us to determine the gravitational
potential of the lens, locally, to several percent accuracy and, combined with
the three independent time delays, measure H_0 to much better than 10%
precision. For this goal, we have developed powerful new lens modeling codes
that make use of the full brightness distribution of the Einstein ring in lens
systems. The B1608+656 system is ideal for our new code. It has precisely
measured time delays, a well-determined stellar velocity dispersion, and an
Einstein ring that is not dominated by the lensed nuclear emission of the
background source. When combined with high-SNR images of Einstein rings, the
new modeling codes provide qualitatively different and much improved analysis
of the ring emission than was previously possible. The proposed ACS
observations will reach the SNR at which the new modeling code can be fully
exploited (SNR=5 per pixel). Our simulations show that these new data will
allow us to reduce the total uncertainties in H_0 derived from the system by
at least a factor of two, to the 5-7% level for this system.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 10159
Title: Characterizing the Sources Responsible for Cosmic
Reionization
PI: Richard Ellis
PI Institution: California Institute of Technology
Our group has demonstrated the role that massive clusters of galaxies, acting
as powerful cosmic lenses, can play in locating sources with modest mass and
star formation rate beyond redshifts z~5-6 likely to be representative of
those responsible for cosmic reionization. The large magnifications, possible
in the critical regions of well-constrained clusters, bring sources into view
that would lie at or beyond the limits of conventional exposures such as the
UDF. Recently, using deep ACS and NICMOS imaging, we have located a low mass
source at z=7.05 whose UV continuum slope is apparently steeper than for
normal star-forming galaxies. We propose a deep ACS grism exposure to confirm
the nature of this source and further ACS and NICMOS imaging of well-studied
clusters to locate further examples. The grism spectroscopy will conclusively
determine the UV SED of this source and our 3-color survey will constrain the
redshift, star-formation rate, and SED of additional 66.5, with more than 2.5 Msun/yr of star formation (our survey
limit). Before the advent of the next generation of observational facilities,
our search technique may represent the only way to reliably select and
characterize the likely population of galaxies during the epoch of
reionization.
================================================================================
Proposal Category: GO
Scientific Category: AGN/QUASARS
ID: 10160
Title: The nuclear scattering geometry of Seyfert galaxies
PI: Andrew Robinson
PI Institution: Rochester Institute of Technology
Orientation-based unification schemes are now well-established as the basis
for understanding the relationships between different classes of AGN. However,
our recent study of the optical polarization properties of Seyfert 1 galaxies
indicates that scattered light emerging from these objects often follows a
different path to that in Seyfert 2's, indicating that the simplest
unification geometry is incomplete. We have developed a generic scattering
model for Seyfert nuclei which includes a compact, equatorial scattering
region located within the circum-nuclear torus and the 'classic' polar
scattering region outside it. We propose to test this model by using NICMOS to
make NIR imaging observations that will allow us to isolate the two scattering
regions within individual objects.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10161
Title: Fresh ammonia-ice on Jupiter: The northern equatorial
region.
PI: Michael Wong
PI Institution: University of California - Berkeley
The proposed multi-band imaging of one of the most dynamic regions on Jupiter
will complement recent space-based infrared datasets and will provide crucial
constraints to models of Jovian atmospheric dynamics. NICMOS is sensitive to
the jovian troposphere at and above the visible cloud decks. We selected six
NICMOS filters with varying levels of atmospheric opacity to observe cloud
features as they rotate from the central meridian to the limb, a strategy that
will maximize the vertical resolution of our retrievals of cloud heights, haze
opacity, and gaseous ammonia concentration. With these filters and the
excellent NICMOS spatial resolution (nearly an order of magnitude improvement
over Galileo NIMS images of the northern equatorial region), we will determine
the smaller-scale structure of fresh NH3 clouds and provide cloud heights as
constraints for models of convection and dynamics associated with 5-micron
hotspots. HST is essential for this project, since no other observatory can
provide the necessary spatial resolution, and no ground-based or space-based
telescopes can observe the ammonia bands we have selected.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10162
Title: Resolving the Thermal Conduction Front in the Bubble S308
PI: You-Hua Chu
PI Institution: University of Illinois at Urbana - Champaign
Heat conduction is one of the most fundamental processes in the interstellar
and intergalactic media. Many astronomical systems contain cool (<10^4 K) gas
in contact with hot (10^6 -10^8 K) gas; at the contact surfaces, heat
conduction occurs and may play an essential role in the thermal structure and
evolution of the system. Observations of thermal conduction fronts have been
extremely limited. Conventionally observations use absorption lines of
collisionally ionized high ions as tracers of 1-3x10^5 K gas in the conduction
front. Such observations allow the determination of column densities but not
the relative locations of these tracer ions. Emission-line observations of a
clear-cut, edge-on conduction front are needed to study the physical structure
of a thermal conduction front. We have identified a clean-cut, edge-on
conduction front in the circumstellar bubble S308, using XMM-Newton X-ray
observations and ground-based optical images and spectra. We request HST STIS
spectroscopic observations of the NV and CVI emission lines in the transition
region from the hot interior gas to the cool nebular shell. These
observations, combined with our complementary observations at optical, FUV,
and X-ray wavelength, allow us to determine the spatially-resolved temperature
profile of a thermal conduction front. Comparisons with models further allow
us to assess the efficiency of thermal conduction.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 10163
Title: Weighing the Most Luminous Main-Sequence Star in the
Galaxy
PI: Anthony Moffat
PI Institution: Universite de Montreal
NGC 3603 is the most massive, visible giant HII region in our Galaxy and
virtually a clone of R136, the famous supercluster in the core of the 30 Dor
region in the LMC. NGC 3603 harbors three young, extremely luminous, hot stars
which mimic the spectral appearance of WN6ha stars. As tailored atmosphere
analysis reveals, these stars are unevolved, very massive stars on the main
sequence. In fact, these stars have the potential of being the most massive
main sequence stars known in our Galaxy. One of these WN6ha stars is a double-
eclipsing binary with a 3.772(3)d period. We propose here to use HST/STIS to
carry out, for the first time, repeated, high-quality spectroscopy of this
binary in order to derive Keplerian orbits for both components and thus
directly measure their masses. Additional photometry will considerably refine
the solution for the inclination angle. Whether or not the mass of the WN6ha
(and possibly also its companion) star significantly exceeds 60 M_sol, the
current directly-observed, upper limit of main sequence stars, will allow us
to put models for massive stars to the test. As a by-product of our
observations, we will also monitor the two remaining WN6ha stars in NGC 3603.
At least one of them shows strong indications for binarity.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10164
Title: HD 62542: Probing the Bare, Dense Core of an
Interstellar Cloud
PI: Daniel Welty
PI Institution: University of Chicago
The line of sight to HD 62542 is remarkable for its unusual UV extinction,
high column densities of various molecules, and apparent dearth of diffuse
atomic gas. The main interstellar cloud appears to be a small, dense (n_H ~
500--1000 cm^-3), molecular knot whose more diffuse outer layers have been
stripped away by stellar winds and shocks. As such, it provides an ideal
venue for investigating the properties of dense, molecular gas --- with
minimal confusion from any associated diffuse gas. We propose to obtain high
resolution, moderately high S/N STIS spectra of C I, CO and its isotopomers,
C_2, C II, O I, and many other atomic species. Those data will be used to
compare various diagnostics of the physical conditions (e.g., C I and O I
fine structure exciattion, CO and C_2 rotational excitation), to determine the
relative abundances of the various CO isotopomers (fractionation), and to
determine the depletions of various elements in dense gas (the predicted
severe depletions have likely been masked by associated diffuse gas in other
cases). Understanding the fractionation and excitation of CO in this
relatively simple case will aid in understanding its behavior in other more
complex regions (important because CO and its isotopomers are often used to
trace and characterize molecular gas when H_2 cannot be measured).
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10165
Title: Determination of orbits and colors for two new binaries
in the Koronis asteroid family
PI: William Merline
PI Institution: Southwest Research Institute
We propose to measure color and orbital properties of two asteroid binaries in
the Koronis family discovered in our SNAP-9747 survey. The best previously
studied asteroid binary system, Ida/Dactyl, is also in the Koronis family.
Differential space weathering measured on the Ida and Dactyl surfaces has been
a powerful constraint on models of satellite formation mechanisms and
satellite survivability. HST offers the unique opportunity for similar
measurements of these much smaller, main-belt binaries. The new satellites
are believed to have formed through different collisional mechanisms than
Ida/Dactyl. Further, with a set of 4 relative position measurements for each
of the two systems, added to the discovery snapshots, we will determine and
compare the densities of the primaries with Ida (a large, 31.5 km, asteroid
with density 2.6+-0.5 g/cm^3, measured by the Galileo flyby). In contrast,
(17246) and (22899) are 4.5 km bodies that are likely to have been
restructured since the family-forming event by subsequent collisions. As all
are members of the same family, differences in density would constrain bulk
composition and internal structure (e.g. shard vs. rubble-pile). Hence, these
measurements are likely to further elucidate the mechanisms for formation of
satellites.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 10166
Title: ACS and WFPC2 Stellar Photometry in the Kepler Mission
Target Field
PI: William Borucki
PI Institution: NASA Ames Research Center
We will observe three regions at the Galactic Equator (GE) to determine the
areal density of background stars down to apparent visual magnitude 25.
Eclipsing binary stars of this magnitude may confound Kepler photometric data,
which are intended to detect transits of Earth-size planets across foregroud
parent stars. The GE is the region of greatest areal density of target stars,
but there is no information on the numbers of 25th magnitude stars there. The
Kepler mission is obligated to do everything possible to avoid false positive
claims of Earth-size planets, because following missions, such as the
Terrestrial Planet Finder will rely on Kepler findings to optimize their
designs. The proposed observations will guide the Kepler team in their
efforts to avoid false positives. For example, the data could indicate that
it would be better for Kepler to abandon the area of greatest target
opportunity in order to reduce the risk of false positive claims.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10167
Title: Imaging of Ices in Circumstellar Disks
PI: Alycia Weinberger
PI Institution: Carnegie Institution of Washington
The link between the material of the interstellar medium and the ultimate
composition of planets lies in the way gas and dust are processed in
circumstellar disks. Planet formation models rely upon a knowledge of the
disk constituents and temperature profiles to simulate how small grains
eventually combine into terrestrial planets and gas giant cores. Disks around
other stars may be analogs for our own early Solar System and thus allow the
direct measurement of such phenomena. Only recently, however, have well-
resolved images of dust disks around several late T Tauri or main sequence
stars been secured. HST provides a uniquely stable platform for making such
sensitive high dynamic range images. Now, for those handful of disks already
resolved, we are able to go beyond the discovery phase and begin making
astrophysical measurements to deepen our understanding of the course of disk
evolution. We therefore propose a multi-wavelength study with NICMOS designed
to discover the spatial distribution of two common Solar System materials --
methane and water ices -- in other systems.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10168
Title: Spatially Relsoved Spectroscopy of HR 4796A's Dust Ring
PI: Alycia Weinberger
PI Institution: Carnegie Institution of Washington
HST's high-contrast capabilities provide exciting imaging of circumstellar
debris disks with complex structures. In particular, broad-band imaging using
the coronagraphs in NICMOS and STIS has elucidated the disk morphology of HR
4796A exquisitely, but can only provide colors, not detailed compositional
information on its dust. With spectra, we will measure the detailed albedo of
the disk dust over a large wavelength range and search for interstellar
medium-like molecules and water ice. We will also use our spatially resolved
spectra for very high angular resolution profiles of the disk width to
constrain models for planets circling inside the dust. We have demonstrated
in a previous program how to use STIS for spatially resolved disk
spectroscopy. We now propose to use our technique to study HR 4796A.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10169
Title: Star Formation in Luminous Infrared Galaxies: giant HII
Regions and Super Star Clusters
PI: Almudena Alonso-Herrero
PI Institution: Instituto de Estructura de la Materia
Luminous Infrared Galaxies (LIRGs,LIR = 10^11-10^12Lsol) and Ultraluminous
Infrared Galaxies (LIR>10^12Lsol) account for approximately 75% of all the
galaxies detected in the mid-infrared in the redshift range z=0-1.5. In the
local universe it is found that LIRGs are predominantly powered by intense
star formation (SF). However, the physical conditions and processes governing
such dramatic activity over scales of tens to a few hundred parsecs are poorly
known. In the last decade HST has been playing a significant role, mainly with
the discovery of super star cluters (SSCs), and more recently, giant HII
regions. Based on observations of a few LIRGs, we found that these giant HII
regions and associated SSCs appear to be more common in LIRGs than in normal
galaxies, and may dominate the star formation activity in LIRGs. A larger
sample is required to address fundamental questions. We propose an HST/NICMOS
targeted campaign of a volume limited sample (v<5200km/s) of 24 LIRGs. This
proposal will probe the role of giant HII regions in the overall energetics of
the current star formation, their relation to SSCs, and the dependence of star
formation properties on other parameters of LIRGs. Such detailed knowledge of
the SF properties of LIRGs in the local universe is essential for
understanding galaxies at high redshift.
================================================================================
Proposal Category: SNAP
Scientific Category: SOLAR SYSTEM
ID: 10170
Title: Atmospheric Variability 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, months, and years. Uranus is
rapidly approaching equinox in 2007, with another 4 degrees of latitude
becoming visible every year. Recent HST observations during this epoch
(including 6818: Hammel, Lockwood, and Rages; 7885: Hammel, Karkoschka, and
Marley; 8680: Hammel, Rages, Lockwood, and Marley; and 8634: Rages, Hammel,
Lockwood, Marley, and McKay) have revealed strongly wavelength-dependent
latitudinal structure and the presence of numerous visible-wavelength cloud
features in the northern hemisphere. Long-term ground-based observations
(Lockwood and Thompson 1999) show seasonal brightness changes whose origins
are not well understood. Recent near-IR images of Neptune obtained using
adaptive optics on the Keck Telesccope together with images from our Cycle 9
Snapshot program (8634) show a general increase in activity at south temperate
latitudes as well as the possible development of another Great Dark Spot.
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: HOT STARS
ID: 10171
Title: Ultraviolet Spectrum of the Binary Millisecond Pulsar
J0437-4715
PI: George Pavlov
PI Institution: The Pennsylvania State University
PSR J0437-4715 is the nearest and the brightest millisecond (recycled) pulsar,
and the only one detected at near-optical wavelengths. We detected it with the
HST STIS/FUV-MAMA detector and found that its FUV spectrum is consistent with
being emitted from the neutron star surface with a temperature of about 0.1
MK, surprisingly high for such an old object. We also found evidence of an
emission line at 1372 A, tentatively interpreted as a Zeeman component of the
hydrogen Ly-alpha line in a magnetic field of 700 MG. Unfortunately, the
spectrum was imaged in a region of strong detector background, which strongly
hampered the spectral and timing analyses. We propose to re-observe the pulsar
with the FUV-MAMA, placing the target in a low-background region, and also
observe it with the NUV-MAMA to obtain the spectrum and pulsations in a broad
UV range. The spectral analysis will allow us to measure the temperature of
the full neutron star surface and test the origin of the heating of old
neutron stars. Confirmation of the spectral line would lead to a first direct
measuremnt of the magnetic field and radius of a spin-powered neutron star
and uniquely constrain the equation of state of superdense matter. The NUV
spectrum and pulsations will also probe the magnetospheric emission and the
thermal structure of the cool white dwarf companion.
================================================================================
Proposal Category: GO
Scientific Category: STAR FORMATION
ID: 10172
Title: Our Galaxy's most promising Super Star Cluster candidate,
Westerlund 1: Tip of the Iceberg?
PI: Richard de Grijs
PI Institution: University of Sheffield
Recent ground-based observations have revealed that the highly reddened
Galactic cluster Westerlund 1 is the current best and by far the nearest
"Young Massive Star Cluster" (YSC) candidate, i.e. a young (< 10 Myr), dense
and massive (> 10,000 Mo) object of which until recently 30 Doradus in the LMC
was believed to be the nearest example. However, extrapolations of the locally
derived cluster luminosity function indicate that perhaps up to a hundred
similar objects should exist within the Galaxy. The close-up view of a YSC
provided by Westerlund 1 allows us to obtain an unprecedented glimpse of the
process of massive cluster formation, evolution and fate, which are among the
very key issues in modern astrophysics. Utilising deep ACS and NICMOS imaging
and sophisticated N-body and Monte Carlo simulations, we will address key
questions regarding Westerlund 1's nature, formation and dynamical evolution.
These include, What are the initial conditions with which Westerlund 1 was
born? To what degree was mass segregation really primordial? Has the binary
fraction changed during the short cluster lifetime? Do we expect the cluster
to have a population of stellar-mass black holes? Does the cluster harbour an
intermediate-mass black hole in its core? Is Westerlund 1 unique as a Galactic
YSC? How similar is the cluster to the massive "Arches" and "Quintuplet"
Galactic Centre clusters, and to 30 Doradus? With an expected life-span of >
100 Myr, it is conceivable that there should be more YSCs like Westerlund 1 in
the Galactic disk. Our dynamical simulations will help us determine the
ultimate fate of such clusters, allowing us to at least begin to answer the
question of Westerlund 1's uniqueness in the context of the Galaxy's stellar
populations.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN/QUASARS
ID: 10173
Title: Infrared Snapshots of 3CR Radio Galaxies
PI: William Sparks
PI Institution: Space Telescope Science Institute
Radio galaxies are an important class of extragalactic objects: they are one
of the most energetic astrophysical phenomena and they provide an exceptional
probe of the evolving Universe, lying typically in high density regions but
well-represented across a wide redshift range. In earlier Cycles we carried
out extensive HST observations of the 3CR sources in order to acquire a
complete and quantitative inventory of the structure, contents and evolution
of these important objects. Amongst the results, we discovered new optical
jets, dust lanes, face-on disks with optical jets, and revealed point-like
nuclei whose properties support FR-I/BL Lac unified schemes. Here, we propose
to obtain NICMOS infrared images of 3CR sources with z<0.3 as a major
enhancement to an already superb dataset. We aim to deshroud dusty galaxies,
study the underlying host galaxy free from the distorting effects of dust,
locate hidden regions of star formation and establish the physical
characteristics of the dust itself. We will measure frequency and spectral
energy distributions of point-like nuclei, expected to be stronger and more
prevelant in the IR, seek spectral turnovers in known synchrotron jets and
find new jets. We will strongly test unified AGN schemes and merge these data
with existing X-ray to radio observations. The resulting database will be an
incredibly valuable resource to the astronomical community for years to come.
================================================================================
Proposal Category: SNAP
Scientific Category: GALAXIES
ID: 10174
Title: Dark-matter halos and evolution of high-z early-type
galaxies
PI: Leon Koopmans
PI Institution: Kapteyn Astronomical Institute
Gravitational lensing and stellar dynamics provide two complementary methods
to determine the mass distribution and evolution of luminous and dark-matter
in early-type (E/S0) galaxies. The combined study of stellar dynamics and
gravitational lensing allows one to break degeneracies inherent to each method
separately, providing a clean probe of the internal structure of massive
galaxies. Since most lens galaxies are at redshifts z=0.1-1.0, they also
provide the required look-back time to study their structural and stellar-
population evolution. We recently analyzed 5 E/S0 lens galaxies between z=0.5
and 1.0, combining exquisite Hubble Space Telescope imaging data with
kinematic data from ground-based Keck spectroscopy, placing the first precise
constraints on the dark-matter mass fraction and its inner slope beyond the
local Universe. To expand the sample to ~30 systems -- required to study
potential trends and evolution in the E/S0 mass profiles -- we propose to
target the 49 E/S0 lens-galaxy candidates discovered by Bolton et al. (2004)
from the Sloan Digital Sky Survey (SDSS). With the average lens rate being 40%
and some systems having a lensing probability close to unity, we expect to
discover ~20 strong gravitational lenses from the sample. This will triple the
current sample of 9 E/S0 systems, with data in hand. With the sample of 30
systems, we will be able to determine the average slope of the dark-matter and
total mass profile of E/S0 galaxies to 10% and 4% accuracy, respectively. If
present, we can simultaneously detect 10% evolution in the total mass slope
with 95% confidence. This will provide unprecedented constraints on E/S0
galaxies beyond the local Universe and allow a stringent test of their
formation scenarios and the standard cosmological model.
================================================================================
Proposal Category: SNAP
Scientific Category: HOT STARS
ID: 10175
Title: STIS Snapshot Survey of Boron Abundances in Early-B Stars
PI: Charles Proffitt
PI Institution: Catholic University of America
Boron abundances in massive stars provide a unique constraint for new
theoretical models of stellar evolution that include rotation. We propose to
use STIS to measure the B III doublet near 2066 Angstroms in a large sample
of early-B stars. A high priority will be placed on obtaining abundances for
several stars in each of a number of different young clusters, assocations,
and star forming regions. This will allow quantitative comparision with
theoretical predictions of rotationally driven mixing in early B stars as
function of mass, age, and rotation rate. Since boron abundance measurements
are not possible for large vsin(i) values, and sin(i) is not known for
individual stars, a large sample is required to statistically test the
predictions of boron depletion as a function of the true rotation rate.
For bright nearby stars (25 targets) we will use the G230MB grating and obtain
very high S/N (>200:1). This avoids the need for an ND filter which would
discard 99% of the photons. Spectral synthesis techniques will allow us to
derive accurate abundances despite the moderate resolution of this grating,
even for stars with relatively high vsin(i) values. This is especially
important in testing rotational models, as current abundance measurements are
mostly for stars with much lower than average rotation rates. For fainter,
more distant stars (27 targets) we will use the E230M or E230H grating with
the 0.2x0.2 aperture.
================================================================================
Proposal Category: GO
Scientific Category: STAR FORMATION
ID: 10176
Title: Coronagraphic Survey for Giant Planets Around Nearby
Young Stars
PI: Inseok Song
PI Institution: University of California - Los Angeles
A systematic imaging search for extra-solar Jovian planets is now possible
thanks to recent progress in identifying "young stars near Earth". For most of
the proposed young (<~ 30 Myrs) and nearby (<~ 60 pc) targets, we can detect a
few Jupiter-mass planets as close as a few tens of AUs from the primary stars.
This represents the first time that potential analogs of our solar system -
that is planetary systems with giant planets having semi-major axes comparable
to those of the four giant planets of the Solar System - come within the grasp
of existing instrumentation. Our proposed targets have not been observed for
planets with the Hubble Space Telescope previously. Considering the very
successful earlier NICMOS observations of low mass brown dwarfs and planetary
disks among members of the TW Hydrae Association, a fair fraction of our
targets should also turn out to posses low mass brown dwarfs, giant planets,
or dusty planetary disks because our targets are similar to (or even better
than) the TW Hydrae stars in terms of youth and proximity to Earth. Due to
the recent cancellation of SM4, HST will inevitably degrade into a 2-gyro mode
soon and high contrast survey programs like our own cannot be carried out with
two gyros. This means that the HST cycle 13 may be the last chance to find
young Solar System analogs in the coming decade. Should HST time be awarded
and planetary mass candidates be found, proper motion follow-up of candidate
planets will be done with ground-based AOs.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10177
Title: Solar Systems In Formation: A NICMOS Coronagraphic
Survey of Protoplanetary and Debris Disks
PI: Glenn Schneider
PI Institution: University of Arizona
Until recently, despite decades of concerted effort applied to understanding
the formation processes that gave birth to our solar system, the detailed
morphology of circumstellar material that must eventually form planets has
been virtually impossible to discern. The advent of high contrast,
coronagraphic imaging as implemented with the instruments aboard HST has
dramatically enhanced our understanding of natal planetary system formation.
Even so, only a handful of evolved disks (~ 1 Myr and older) have been imaged
and spatially resolved in light scattered from their constituent grains. To
elucidate the physical processes and properties in potentially planet-forming
circumstellar disks, and to understand the nature and evolution of their
grains, a larger spatially resolved and photometrically reliable sample of
such systems must be observed. Thus, we propose a highly sensitive
circumstellar disk imaging survey of a well-defined and carefully selected
sample of YSOs (1-10 Myr T Tau and HAeBe stars) and (> app 10 Myr) main
sequence stars, to probe the posited epoch of planetary system formation, and
to provide this critically needed imagery. Our resolved images will shed
light on the spatial distributions of the dust in these thermally emissive
disks. In combination with their long wavelength SEDs the physical
properties of the grains will be discerned, or constrained by our
photometrically accurate surface brightness sensitivity limits for faint
disks which elude detection. Our sample builds on the success of the
exploratory GTO 7233 program, using two-roll per orbit PSF-subtracted NICMOS
coronagraphy to provide the highest detection sensitivity to the smallest
disks around bright stars which can be imaged with HST. Our sample will
discriminate between proposed evolutionary scenarios while providing a legacy
of cataloged morphologies for interpreting mid- and far-IR SEDs that the
recently launched Spitzer Space Telescope will deliver. This project cannot
be done from the ground, and becomes untenable for HST after Cycle 13 under
the anticipated use of two-gyro pointing control mode.
================================================================================
Proposal Category: GO
Scientific Category: STAR FORMATION
ID: 10178
Title: Imaging Polarimetry of Young Stellar Objects with ACS and
NICMOS: A study in dust grain evolution
PI: Dean Hines
PI Institution: Space Science Institute
The formation of planetary systems is intimately linked to the dust population
in circumstellar disks, thus understanding dust grain evolution is essential
to advancing our understanding of how planets form. By combining (1) the high
resolution polarimetric capabilities of ACS and NICMOS, (2) powerful 3-D
radiative transfer codes, and (3) observations of objects known to span the
earliest stellar evolutionary phases, we will gain crucial insight into the
initial phases of dust grain growth: evolution away from an ISM distribution.
Fractional polarization is a strong function of wavelength, therefore by
comparing polarimetric images in the optical and infrared, we can sensitively
constrain not only the geometry and optical depth of the scattering medium,
but also the grain size distribution. By observing objects representative of
the earliest evolutionary sequence of YSOs, we will be able to investigate how
the dust population evolves in size and distribution during the crucial
transition from a disk+envelope system to a disk+star system. The proposed
study will help to establish the fundamental time scales for the initial
depletion of ISM-like grains: the first step in understanding the
transformation from small submicron sized dust grains, to large millimeter
sized grains, and untimely to planetary bodies.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10179
Title: A Coordinated NICMOS and XMM Experiment to Observe the
Variability of Sgr A*
PI: Farhad Yusef-Zadeh
PI Institution: Northwestern University
The massive black hole Sgr A* at the Galactic center has recently shown not
only quiescent emission at near-IR wavelengths, but also flare activity with
quasi-periodicity of 17 minutes. Our research group has been granted two
blocks of observing time with XMM-Newton to monitor the spectral and temporal
properties of Sgr A*. Simultaneously with these X-ray observations, we will
also monitor Sgr A* at radio, submillimeter, near-IR, and gamma-ray
wavelengths. We propose to use NICMOS in parallel with the XMM observations to
provide evidence of a well-defined minimum periodicity in the spectrum of
flare periodicities. This, combined with periodicity in the near-IR line
emission, would strengthen the claim that the emitting gas resides at the
innermost stable circular orbit around the GC black hole, thus measuring the
spin parameter of a massive black hole. Current groundbased near-IR data
suggest a spin parameter of ~0.5. In addition, the correlation pattern of
emission over a wide spectrum would elucidate a key issue of how to explain
the low luminosity of Sgr A*. The NICMOS on HST is the only instrument that
can accurately measure the 17 minute quasi-periodic variability of Sgr A*
because of the long time baseline over which HST can observe Sgr A* in
parallel with XMM-Newton.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10180
Title: Ultracompact Blue Dwarfs: Galaxy Formation in the Local
Universe?
PI: Michael Corbin
PI Institution: Computer Sciences Corporation
Recent observations suggest that very low-mass galaxies in the local universe
are still in the process of formation. To investigate this issue we propose
to obtain deep ACS HRC images in the U, V and I bands of a sample of 11
"ultracompact" blue dwarf galaxies (UCBDs) identified in the Sloan Digital Sky
Survey. These objects are nearby (z < 0.009), actively star-forming, and have
extremely small angular and physical sizes (d < 6" and D < 1 kpc). They also
tend to reside in voids. Our WFPC2 images of the prototype object of this
class, POX 186, reveal this tiny object to have a highly disturbed morphlogy
indicative of a recent (within 10^8 yr) collision between two small (~ 100 pc)
clumps of stars that could represent the long-sought building blocks predicted
by the Press-Schechter model of hierarchical galaxy formation. This collision
has also triggered the formation of a "super" star cluster (SSC) at the
object's core that may be the progenitor of a globular cluster. POX 186 thus
appears to be a very small dwarf galaxy in the process of formation. This
exciting discovery strongly motivates HST imaging of a full sample of UCBDs in
order to determine if they have morphologies similar to POX 186. HST images
are essential for resolving the structure of these objects, including
establishing the presence of SSCs. HST also offers the only way to determine
their morphologies in the near UV. The spectra of the objects available from
the SDSS will also allow us to measure their star formation rates, dust
content and metallicities. In addition to potentially providing the first
direct evidence of Press-Schechter building blocks, these data could yield
insight into the relationship between galaxy and globular cluster formation,
and will serve as a test of the recent "downsizing" model of galaxy formation
in which the least massive objects are the last to form.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10181
Title: ACS/NICMOS Imaging of Bright Lyman Break Galaxy
Candidates from SDSS
PI: Misty Bentz
PI Institution: Ohio State University
The recent surprising discovery of six unusually bright (r~20 mag) Lyman break
galaxy (LBG) candidates with z=2.45-2.80 in the Sloan Digital Sky Survey
(SDSS) raises a number of questions that only HST can address. Specifically,
what is the true nature of these objects, and what role if any is played by
gravitational lensing? We propose to use the superior resolution and
sensitivity of ACS and NICMOS to obtain deep images of these objects and their
environments. Compared to SDSS images, HST will allow us to determine their
morphologies (extended, point-source, or lensed), the appearance of their
environments (rich or poor), and to detect any faint foreground groups or
clusters that might be responsible for lensing these objects. All outcomes
would be intruiging. If the objects are lensed, it increases from 1 (MS1512-
cB58) to 7 the number of normal LBGs bright enough to study individually. If
they are instead unlensed point sources, they will represent a new class of
previously unidentified absorption-line quasars. Finally, if they are
unlensed and extended star-forming galaxies, they are at least 4mag brighter
than L_* LBGs, thus making them the most luminous star-forming objects yet
seen, representing a heretofore unknown extreme population of objects.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 10182
Title: Towards a Comprehensive Understanding of Type Ia
Supernovae: The Necessity of UV Observations
PI: Alex Filippenko
PI Institution: University of California - Berkeley
Type Ia supernovae (SNe Ia) are very important to many diverse areas of
astrophysics, from the chemical evolution of galaxies to observational
cosmology which led to the discovery of dark energy and the accelerating
Universe. However, the utility of SNe Ia as cosmological probes depends on the
degree of our understanding of SN Ia physics, and various systematic effects
such as cosmic chemical evolution. At present, the progenitors of SNe Ia and
the exact explosion mechanisms are still poorly understood, as are
evolutionary effects on SN Ia peak luminosities. Since early-time UV spectra
and light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: (1) Detailed
studies of two very bright, young, nearby SNe Ia with HST UV spectroscopy at
13 epochs within the first 1.5 months after discovery; and (2) studies of
correlations with luminosity for five somewhat more distant Hubble-flow SNe
Ia, for which relative luminosities can be determined with precision, using 8
epochs of HST UV spectroscopy and/or broad-band imaging. The HST data, along
with extensive ground-based optical to near-IR observations, will be analyzed
with state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the next
phase of precision cosmology measurements using SNe Ia, allowing us to more
fully capitalize on the substantial past (and future) investments of time made
with HST in observations of high-redshift SNe Ia.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 10183
Title: A Deep Far-UV Search for the Interacting Binary
Population in M80
PI: Christian Knigge
PI Institution: University of Southampton
We propose to carry out a deep, far-ultraviolet (FUV), time-resolved survey
for cataclysmic variables (CVs) and other dynamically-formed objects in the
globular cluster (GC) M80. This will include a search for FUV counterparts to
the 17 Chandra sources in our field of view, which include 2 LMXBs and 5 X-ray
selected CV candidates. Our goal is to confirm these sources as interacting
binaries and find any additional CVs below the Chandra detection limit. We
will achieve this with 6 orbits of FUV imaging with the ACS/SB, plus one
additional orbit of NUV imaging with ACS/HRC. Since crowding is not a problem
in the FUV, this will yield time-resolved FUV photometry of all blue objects
in the cluster core. Our CV census will be both deep enough to be essentially
complete and ``broad'' enough to involve all of the following CV
characteristics: (1) UV brightness; (2) blue FUV spectral shape; (3) strong
CIV and HeII emission; (4) short time-scale ($\sim$ minutes) variability
(flickering, WD spin); (6) intermediate time-scale ($\sim$ hours) variability
(orbital variations); (7) long time-scale ($\sim$ weeks) variability (dwarf
nova eruptions). We will thus uncover the interacting binary population in
M80. In addition, our survey will detect numerous blue stragglers and hot
white dwarfs, as well as any other blue objects in the central regions of this
cluster.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 10184
Title: A New Class of Bright Ultraviolet Variable Sources in the
Globular Cluster NGC 1851
PI: David Zurek
PI Institution: American Museum of Natural History
Our reductions of archival STIS/FUV-MAMA data (AR9225) have discovered 13
completely unexpected and unexplained Ultraviolet bright variables. Eleven of
the variables have been identified with evolved stars (Horizontal Branch or
Asymptotic Giant Branch). The total number and nature of these systems is
completely unknown. If these variables are binaries the implication is that
the binary fraction (up to 25%) in NGC 1851 is the highest in all Galactic
globular clusters. The radial distributions of the variables and the blue
horizontal branch stars imply a common origin and perhaps an explanation of
the bi-modal morphology of the horizontal branch in the color magnitude
diagrams of globular clusters. These variables may be the tip of the iceberg
and a critical clue concerning the infamous "second parameter". We propose to
observe NGC 1851 on three occasions with the same setup as the archival data
to determine the total number and periods of the ultraviolet variables.
================================================================================
Proposal Category: SNAP
Scientific Category: COOL STARS
ID: 10185
Title: When does Bipolarity Impose itself on the Extreme Mass
Outflows from AGB Stars? An ACS SNAPshot Survey
PI: Raghvendra Sahai
PI Institution: Jet Propulsion Laboratory
Essentially all well-characterized preplanetary nebulae (PPNe) -- objects in
transition between the AGB and planetary nebula evolutionary phases - are
bipolar, whereas the mass-loss envelopes of AGB stars are strikingly
spherical. In order to understand the processes leading to bipolar mass-
ejection, we need to know at what stage of stellar evolution does bipolarity
in the mass-loss first manifest itself? Our previous SNAPshot surveys of a
PPNe sample (with ACS & NICMOS) show that roughly half our targets observed
are resolved, with well-defined bipolar or multipolar morphologies.
Spectroscopic surveys of our sample confirm that these objects have not yet
evolved into planetary nebulae. Thus, the transformation from spherical to
aspherical geometries has already fully developed by the time these dying
stars have become preplanetary nebulae. From this new and surprising result,
we hypothesize that the transformation to bipolarity begins during the very
late AGB phase, and happens very quickly, just before, or as the stars are
evolving off the AGB. We propose to test this hypothesis
quantitatively, through a SNAPshot imaging survey of very evolved AGB stars
which we believe are nascent preplanetary nebulae; with our target list being
drawn from published lists of AGB stars with detected heavy mass-loss (from
millimeter-wave observations). This survey is crucial for determining how and
when the bipolar geometry asserts itself. Supporting kinematic observations
using long-slit optical spectroscopy (with the Keck), millimeter and radio
interferometric observations (with OVRO, VLA & VLBA) are being undertaken. The
results from this survey (together with our previous work) will allow us to
draw general conclusions about the onset of bipolar mass-ejection during late
stellar evolution, and will provide crucial input for theories of post-AGB
stellar evolution. Our survey will produce an archival legacy of long-standing
value for future studies of dying stars.
================================================================================
Proposal Category: SNAP
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 10186
Title: A Lyman-alpha Snapshot Survey of FBS and SBS Galaxies
PI: Claus Leitherer
PI Institution: Space Telescope Science Institute
Search strategies for primeval galaxies rely on the assumption that Lyman-
alpha can be powered by photoionization from hot stars. Theoretical models,
however, indicate that Lyman-alpha is far from being a pure recombination
line: absorption and scattering in the interstellar medium and the kinematics
of outflowing gas make firm predictions for the Lyman-alpha strength
difficult. Therefore observational tests are required. A sample of 42 galaxies
with active star formation has been selected from the First and Second
Byurakan Survey to perform such a test. The target galaxies belong to the
spectral class s1, implying they are H II galaxies, blue compact dwarfs, or
nuclear starbursts. This sample is optimized to address whether local
starbursts are strong Lyman-alpha emitters. We propose to obtain STIS G140L
spectra of the galaxies in order to detect Lyman-alpha emission with
equivalent widths larger than 5 Angstroms in this statistically significant,
homogeneous sample. We will utilize the existing, extensive body of ground-
based data to model the stellar population and make a prediction for the
Lyman-alpha emission assuming pure recombination and no radiative transfer
effects by gas and dust. Comparison with the observations will provide
constraints on such effects. The scientific goals are twofold: First, we make
an effort to understand how an apparently simple line, such as Lyman-alpha,
can be affected by radiative transfer effects and geometries in the
interstellar medium of typical star-forming regions. Second, the proposed
study will serve as an empirical test for the probability to succeed in
detecting Lyman-alpha in more distant systems. Therefore, a high-level goal of
this project is to provide guidelines for search strategies for primeval
galaxies at high redshift. This project is ideally suited for execution in
Snapshot mode.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 10187
Title: Direct imaging of the progenitors of massive, core-
collapse supernovae
PI: Stephen Smartt
PI Institution: University of Cambridge
Modern supernovae searches in the nearby Universe are discovering large
numbers of SNe which have massive star progenitors (Types II, Ib and Ic). The
extensive HST image archives of galaxies within ~20Mpc enables their
individual bright stellar content to be resolved. As massive, evolved stars
are the most luminous single objects in a galaxy, the progenitors of core-
collapse SNe should be directly detectable on pre-explosion images. In our
ongoing HST programme we have detected the first red supergiant progenitor of
a normal type II supernova, shown that SN 1993J came from a binary system, and
set direct mass-limits on three other type II supernovae progenitors. These
discoveries are providing strong constraints on theoretical models of pre-
supernova stellar evolution that predict which stars produce which type of
supernovae. We request time to continue this successful project, and require
ACS observations of future SNe which are discovered in galaxies closer than
20Mpc which have pre-explosion HST archive images available. These
observations will allow the SNe to be precisely positioned on the pre-
explosion frames with the required astrometric accuracy of around 0.05", and
provide 3-colour photometry of the surrounding stellar populations for
reddening estimations. The goal of this project is to directly identify the
progenitor stars of core-collapse supernovae. We will compare the results to
our own stellar evolutionary tracks in order to determine masses or
restrictive mass-limits for the progenitors.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10188
Title: In-Depth Study of The Antennae with NICMOS and ACS
PI: Bradley Whitmore
PI Institution: Space Telescope Science Institute
We propose new observations of "The Antennae" (NGC 4038/39), the nearest and
youngest example of a major disk-disk merger, with NICMOS and ACS. The long
overdue NICMOS observations will allow us to penetrate the dust in the Overlap
Region, measure the P_alpha emission and CO band strengths of young clusters,
and study supernova remnants in heavily obscured regions using [FeII] images.
The high resolution (0.05" pixel) ACS observations will allow us for the
first time to reliably distinguish clusters from stars based on their apparent
sizes, and to potentially identify hundreds of supernova remnants that may
control the energy balance and feedback mechanisms within the ISM (based on
[SII] images). In conjunction with our previous WFPC2, GHRS, and STIS
observations, the new data will provide answers to fundamental questions such
as: How do these clusters form and evolve? How quickly are they destroyed and
what fraction of the field stars were formed in clusters. How many clusters
are hidden by dust? How do the clusters and associated supernovae affect
the local and global ISM? What are the dynamical masses of the clusters, and
are the stellar IMF's truncated? Simultaneous parallel observations will
also determine whether clusters can form in the more quiescent environment of
the inner tails. A better understanding of how mergers form tremendous numbers
of clusters and stars in the local universe will help shed light on processes
that are crucial during galaxy assembly throughout the observable universe.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 10189
Title: PANS-Probing Acceleration Now with Supernovae
PI: Adam Riess
PI Institution: Space Telescope Science Institute
Type Ia supernovae (SNe Ia) provide the most direct evidence for an
accelerating Universe, a result widely attributed to dark energy. Using HST in
Cycle 11 we extended the Hubble diagram with 6 of the 7 highest-redshift SNe
Ia known, all at z>1.25, providing conclusive evidence of an earlier epoch of
cosmic deceleration. The full sample of 16 new SNe Ia match the cosmic
concordance model and are inconsistent with a simple model of evolution or
dust as alternatives to dark energy. Understanding dark energy may be the
biggest current challenge to cosmology and particle physics. To understand
the nature of dark energy, we seek to measure its two most fundamental
properties: its evolution (i.e., dw/dz), and its recent equation of state
(i.e., w(z=0)). SNe Ia at z>1, beyond the reach of the ground but squarely
within the reach of HST with ACS, are crucial to break the degeneracy in the
measurements of these two basic aspects of dark energy. The SNe Ia we have
discovered and measured with HST in Cycle 11, now double the precision of our
knowledge of both properties. Here we propose to quadruple the sample of SNe
Ia at z>1 in the next two cycles, complementing on-going surveys from the
ground at z<1, and again doubling the precision of dark energy constraints.
Should the current best fit model prove to be the correct one, the precision
expected from the current proposal will suffice to rule out a cosmological
constant at the 99% confidence level. Whatever the result, these objects will
provide the basis with which to extend our empirical knowledge of this newly
discovered and dominant component of the Universe, and will remain one of the
most significant legacies of HST. In addition, our survey and follow-up data
will greatly enhance the value of the archival data within the target Treasury
fields for galaxy studies.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 10190
Title: The Star Formation History and Metallicity Evolution of
M33: A Comprehensive Study of Disk Evolution
PI: Donald Garnett
PI Institution: University of Arizona
We will obtain deep, panchromatic imaging photometry of stellar populations in
four fields ranging from 0.5 to 4 scale lengths across the disk of the Local
Group spiral M33. The observations are designed to detect the oldest main-
sequence turnoffs in three outer disk fields, and to reach the crowding limit
in the innermost field. We will combine the photometry data with information
we already have in-hand on abundances from stars and H II regions in M33 to
derive the star formation history and metallicity evolution of the M33 disk.
The information from our four fields will allow us to obtain (1) the ages of
the oldest disk stars and the radial variation of their ages; (2) the radial
variation of the star formation history and its nature (e.g., constant,
declining, or bursting); and (3) the metallicity distribution in each field
and the time evolution of the metallicity gradient. Our team, an experienced
mix of photometrists, spectroscopists, and galaxy evolution theorists, will
use the results from this program to construct a comprehensive chemo-dynamical
model for the M33 disk. This detailed study of M33 will be a key in developing
an understanding of the formation and evolution of disks that can be applied
to studies of disks at both low and high redshift, and will also yield a