Cycle
16 Abstract catalog (based on Phase I submissions)
Generated
on:
Mon
Apr 9 12:08:20 EDT 2007
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11099
Title:
A
"silver bullet" for the sources of reionization
PI:
Marusa
Bradac
PI
Institution:
Stanford
University
Recent
discoveries of z>6 galaxies have given us the first glimpse of the
Universe
shortly after the era of reionization. The questions arose whether
these
first galaxies can be made responsible for the reionization process, and
how
long did it last. Neither observations nor theory provide a clean
answer.
In
particular observations give results that are barely mutually consistent
and
need to be further tested. Observing high redshift (z>7) sources is
in
general
difficult, mostly due to the high luminosity distance to these
objects,
and partly due to the lower expected stellar masses compared to
objects
at moderate redshifts. We
propose to use one of the most massive,
merging
cluster 1E0657-56 (z=0.295) as a cosmic telescopes to efficiently
probe
the high-redshift universe. The gravitational potential well of this
cluster
provides several magnitudes of magnification, enabling study of
intrinsically
lower luminosity galaxies.As we discuss in the proposal, due to
its
highly elongated mass distribution and ideal redshift the bullet cluster
is
a prime candidate for this study. We propose deep NICMOS and WFPC2
observations;
with much reduced observing time compared to e.g. NICMOS UDF we
expect
an order of magnitude more (~5 candidates) z>7 objects. They will
also
likely
be multiply imaged, and since the geometry of images depends upon the
redshift,
we will be able to confirm their nature, thereby not requiring
(often
prohibitive at these magnitudes) spectroscopic follow-up. This will
enable
us to count high-redshift sources and constrain their luminosity
function;
a task made possible with the help of gravitational lensing even in
the
pre-JWST era.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11100
Title:
Two
new `bullets' for MOND: revealing the properties of dark matter in
massive
merging clusters
PI:
Marusa
Bradac
PI
Institution:
Stanford
University
The
principal objective of this proposal is to study the physical nature of
dark
matter by using two, massive, newly-identified merging clusters of
galaxies.
As shown by the pioneering example of the ``bullet cluster''
(1E0657-56),
such systems are ideal laboratories for detecting dark matter and
distinguishing
between cold dark matter (CDM) and other scenarios (e.g.
self-
interacting
dark matter). Our limit on the self-interaction cross-section of
dark
matter relies on the assumption of a normal pre-merger mass-to-light
ratios,
and a small impact parameter during the collision of the two clusters.
In
order to mitigate any possible systematic effects, it is vital to extend
this
work to other, similar systems. With detailed observations of new
systems,
the systematic uncertainties in the dark matter cross section
calculations
can be improved substantially, allowing us to move from rough
order
of magnitude estimates to measurements with quantifiable uncertainties
that
can be compared usefully with the predictions from numerical
simulations.
Our
targets are two extraordinary, high-redshift, merging galaxy clusters
recently
discovered by the Massive Cluster Survey (MACS). This
survey is by
far
the best matched to this study, since it selects medium redshift
(optimal
for
gravitational lensing studies) and X-ray luminous (hence massive)
objects.
We
have selected the best candidates with clear evidence for considerable
offsets
between the hot X-ray emitting gas and optically luminous stellar
material.
The two most striking examples are the targets of this proposal. To
pin
down the position of the dark matter component we require high
resolution,
absolutely
calibrated mass maps. The combination of weak and strong lensing
measurements
is needed to attain this goal. This can only be achieved with the
excellent
resolving power of the HST (in combination with wide-field,
multicolor
Subaru data already in hand). We
therefore request multicolor
HST/WFPC2
observations of the two merging clusters. The combination of
constraints
from multiply lensed images (identified via morphology and color
information)
and high-resolution weak lensing data will allow us to construct,
self-consistently,
their mass distribution from the very centers to the
outskirts.
Gravitational lensing thus provides a unique tool transforming
these
clusters into dark matter laboratories. They will supply us with answers
as
to the nature and properties of dark matter, and how it shapes galaxies
and
galaxy
clusters and their evolution through cosmic time.
======================================================================
Proposal
Category: GO
Scientific
Category: AGN/QUASARS
ID:
11101
Title:
The
Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies
PI:
Gabriela
Canalizo
PI
Institution:
University
of California - Riverside
The
majority of QSOs are known to reside in centers of galaxies that look
like
ellipticals.
Numerical simulations have shown that remnants of galaxy mergers
often
closely resemble elliptical galaxies. However, it is still strongly
debated
whether the majority of QSO host galaxies are indeed the result of
relatively
recent mergers or whether they are completely analogous to inactive
ellipticals
to which nothing interesting has happened recently.
To address
this
question, we recently obtained deep HST ACS images for five QSO host
galaxies
that were classified morphologically as ellipticals (GO-10421). This
pilot
study revealed striking signs of tidal interactions such as ripples,
tidal
tails, and warped disks that were not detected in previous studies. Our
observations
show that at least some "elliptical" QSO host galaxies are the
products
of relatively recent merger events rather than old galaxies formed at
high
redshift. However, the question remains whether the host galaxies of
classical
QSOs are truly distinct from inactive ellipticals and whether there
is
a connection between the merger events we detect and the current nuclear
activity.
We must therefore place our results into a larger statistical
context.
We are currently conducting an HST archival study of inactive
elliptical
galaxies (AR-10941) to form a control sample. We now propose to
obtain
deep HST/WFPC2 images of 13 QSOs whose host galaxies are classified as
normal
ellipticals. Comparing the results for both samples will help us
determine
whether classical QSOs reside in normal elliptical galaxies or not.
Our
recent pilot study of five QSOs indicates that we can expect exciting
results
and deep insights into the host galaxy morphology also for this larger
sample
of QSOs. A statistically meaningful sample will help us determine the
true
fraction of QSO hosts that suffered strong tidal interactions and thus,
whether
a merger is indeed a requirement to trigger nuclear activity in the
most
luminous AGNs.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11102
Title:
HST
as a Jovian Climate Satellite
PI:
Imke
de Pater
PI
Institution:
University
of California - Berkeley
In
the past year, there have been striking changes in Jupiter's atmosphere.
Among
these are the Oval BA's change from white to red, two new dark
Disturbances
in the southern hemisphere, and a 30% change (since 1997) in the
aspect
ratio of the potential vorticity anomaly of the GRS (not just its
associated
clouds), as we determined from high-accuracy velocities extracted
from
HST images. The determination of high-accuracy velocities requires both
high-resolution
imaging by HST (or flybys), and our novel adaptation of
Correlation
Image Velocimetry (CIV), a technique that has far greater accuracy
than
the traditional method (of identifying velocity tie-points by hand). Our
proposed
observations will test the hypothesis that these changes in Jupiter
validate
our 2004 prediction:
that
the merger of the 3 White Ovals in 1998-
2000
would lead to climate change on Jupiter. The key is to determine, by
indirect
means, the temperature at the base of
the weather layer, a quantity
that
cannot be observed directly at any wavelength. The new Red Oval BA's
velocities
will be used to test our finding that the color change is due to
global
temperature changes. The change in the GRS's aspect ratio suggests a
large
(at least 20%) change in the shear of the local velocity since 1997. The
latter
can be investigated only by determining Jupiter's current zonal winds.
======================================================================
Proposal
Category: SNAP
Scientific
Category: COSMOLOGY
ID:
11103
Title:
A Snapshot Survey of The Most
Massive
Clusters of Galaxies
PI:
Harald
Ebeling
PI
Institution:
University
of Hawaii
We
propose the continuation of our highly successful SNAPshot survey of a
sample
of 125 very X-ray luminous clusters in the redshift range 0.3-0.7. As
demonstrated
by the 25 snapshots obtained so far in Cycle14 and Cycle15 these
systems
frequently exhibit strong gravitational lensing as well as spectacular
examples
of violent galaxy interactions. The proposed observations will
provide
important constraints on the cluster mass distributions, the physical
nature
of galaxy-galaxy and galaxy-gas interactions in cluster cores, and a
set
of optically bright, lensed galaxies for further 8-10m spectroscopy. All
of
our primary science goals require only the detection and
characterisation
of
high-surface-brightness features and are thus achievable even at the
reduced
sensitivity of WFPC2. Because of their high redshift and thus compact
angular
scale our target clusters are less adversely affected by the smaller
field
of view of WFPC2 than more nearby systems. Acknowledging the broad
community
interest in this sample we waive our data rights for these
observations. Due to a clerical error at STScI
our approved Cycle15 SNAP
program
was barred from execution for 3 months and only 6 observations have
been
performed to date - reinstating this SNAP at Cycle16 priority is of
paramount
importance to reach meaningful statistics.
======================================================================
Proposal
Category: GO
Scientific
Category: AGN/QUASARS
ID:
11104
Title:
The
nature of radio transients
PI:
Avishay
Gal-Yam
PI
Institution:
California
Institute of Technology
We
have conducted the first ever blind, wide-field survey for radio
transients
(Levinson
et al. 2002; Gal-Yam et al. 2006). We have discovered four radio
transients
and explored their nature using radio and optical follow-up
observations.
One is a known pulsar, one is a z~0.1 AGN, and one is most
probably
an optically obscured radio supernova (SN) in the nearby galaxy NGC
4216
(the first such event to be discovered by a wide field radio survey).
The
last
source appears not to be associated with a bright host galaxy (to a
limit
of
R < 24.5 mag). We request 4 orbits of WFPC2 F606W imaging to check
whether
we
can establish an association between this radio transient and any of
three
nearby
faint resolved galaxies we have detected from the ground. If the source
is
associated with any of these galaxies it would represent a new type of
extra-galactic
radio bursts, more luminous than, e.g., radio afterglows of
gamma-ray
bursts. Alternatively, ruling out an association with these galaxies
would
disfavor an extra-galactic nature of this object, and suggest instead
that
this is a radio outburst of a faint Galactic compact object, probably a
new
type of radio-flaring neutron star. If this is the case, the high
luminosity
(9 mJy) and relatively high galactic latitude (33 degrees) of this
source
may indicate it is relatively nearby. This single source represents a
large
population (comparable in sky density to AGN, pulsars, and radio SNe)
and
thus merits intensive study. A modest investment of HST time, leveraged
by
massive
ground-based radio and optical efforts, will allow us to identify a
new
class of radio sources, and complete a census of the variable radio sky
down
to ~6 mJy, leaving no unidentifed objects. This result can be directly
scaled
to predict the number and type of transient sources expected to be
detected
by future surveys with the next generation radio arrays, such as ATA
and
SKA.Since our science critically requires HST's spatial resolution
(rather
than
sensitivity) it is perfectly suited to be carried out with WFPC2.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11105
Title:
The
LBV progenitor of SN 2005gl - a new key to massive star evolution
puzzles
PI:
Avishay
Gal-Yam
PI
Institution:
California
Institute of Technology
The
currently accepted theory regarding the last stages of massive star
evolution
maintains that the evolution of the envelope is coupled to that of
the
stellar core. For this reason, very massive stars are expected to shed
their
outer hydrogen envelopes before they develop large iron cores, and
ultimately,
explode as core-collapse supernovae (SNe). It is therefore a
strict
prediction of current models that massive stars (certainly those above
~40
solar mass) will explode as hydrogen-poor SNe, i.e., of Types Ib and Ic.
In
particular, the class of luminous blue variables (LBVs) such as
eta-Carina,
which
are known to be very massive (up to 100 solar masses and above) are
expected
to lose their entire hydrogen envelopes prior to their ultimate
explosions
as SNe. However, using pre-explosion HST/WFPC2 imaging of the
location
of the recent hydrogen-rich type IIn SN 2005gl, we have identified
(Gal-Yam
et al. 2007) its putative progenitor as a very luminous point source
(with
absolute V magnitude of -10.2). If this is a single star, it must be an
LBV
from luminosity considerations (no other stars are as luminous). If our
progenitor
identification is correct, at least in some cases, massive stars
explode
before losing most of their hydrogen envelope, indicating the core and
envelope
are decoupled, and requiring revision of stellar evolution theory.
Here,
we propose a single-orbit HST observation of the location of SN 2005gl
designed
to test whether the point source we identified as its LBV progenitor
has
indeed disappeared (as expected from a single star) or remained
unchanged
(as
expected, e.g., if it is a compact star cluster). These data are the
last
observational
ingredient required to firmly establish (or refute) the
explosion
of an LBV as a type IIn SN, with fundamental implications for the
theory
of massive star evolution. Since the new data will be compared to pre-
explosion
WFPC2 images, this program is perfectly suited to be carried out
with
the WFPC2 camera.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11106
Title:
Target
of Opportunity Imaging of an Unusual Cloud Feature on Uranus
PI:
Heidi
Hammel
PI
Institution:
Space
Science Institute
The
planet Uranus is demonstrating increased atmospheric activity as it
approaches
its 2007 equinox, perhaps in response to extreme insolation change.
Convective
sites in the planet's southern hemisphere reached unprecedented
altitudes
in 2003 (Hammel et al. 2005, Icarus 175, 284); a bright northern
feature
showed the highest contrast yet detected in an outer planet atmosphere
(Sromovsky
et al. 2007, Icarus, submitted); and a dark atmospheric feature was
detected
by HST for the first time (Hammel et al. 2007, in preparation). The
historical
record makes references to discrete structures (both bright and
dark)
on Uranus during previous equinoctial apparitions (the last equinox
occurred
in 1965). The best amateur
facilities are now just able to resolve
the
disk of Uranus and detect such activity if it is very large or has very
high
contrast. Amateurs also have
access to a great many nights of telescope
time. If a discrete cloud feature on Uranus
is reported through the amateur
network,
we propose to obtain follow-up images with HST's WFPC2.
The proposed
TOO
images will permit determination of detailed structure of the feature at
visible
wavelengths, and will provide vertical and horizontal constraints on
the
feature's scattering properties.
HST is the only facility that can
provide
such information at visible wavelengths.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11107
Title:
Imaging
of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in
the Early
Universe
PI:
Timothy
Heckman
PI
Institution:
The
Johns Hopkins University
We
have used the ultraviolet all-sky imaging survey currently being
conducted
by
the Galaxy Evolution Explorer (GALEX) to identify for the first time a
rare
population
of low-redshift starbursts with properties remarkably similar to
high-redshift
Lyman Break Galaxies (LBGs). These "compact UV luminous
galaxies"
(UVLGs) resemble LBGs in terms of size, SFR, surface brightness,
mass,
metallicity, kinematics, dust, and color. The UVLG sample offers the
unique
opportunity of investigating some very important properties of LBGs
that
have remained virtually inaccessible at high redshift:
their morphology
and
the mechanism that drives their star formation. Therefore, in Cycle 15
we
have
imaged 7 UVLGs using ACS in order to 1) characterize their morphology
and
look
for signs of interactions and mergers, and 2) probe their star formation
histories
over a variety of timescales. The images show a striking trend of
small-scale
mergers turning large amounts of gas into vigorous starbursts (a
process
referred to as dissipational or "wet" merging). Here, we propose to
complete
our sample of 31 LBG analogs using the ACS/SBC F150LP (FUV) and WFPC2
F606W
(R) filters in order to create a statistical sample to study the
mechanism
that triggers star formation in UVLGs and its implications for the
nature
of LBGs. Specifically, we will 1) study the trend between galaxy
merging
and SFR in UVLGs, 2) artificially redshift the FUV images to z=1-4 and
compare
morphologies with those in similarly sized samples of LBGs at the same
rest-frame
wavelenghts in e.g. GOODS, UDF, and COSMOS, 3) determine the
presence
and morphology of significant stellar mass in "pre-burst" stars, and
4)
study their immediate environment. Together with our Spitzer
(IRAC+MIPS),
GALEX,
SDSS and radio data, the HST observations will form a unique union of
data
that may for the first time shed light on how the earliest major
episodes
of
star formation in high redshift galaxies came about.
This proposal was
adapted
from an ACS HRC+WFC proposal to meet the new Cycle 16 observing
constraints,
and can be carried out using the ACS/SBC and WFPC2 without
compromising
our original science goals.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11108
Title:
Near
Infrared Observations of a Sample of z~6.5-6.7 Galaxies
PI:
Esther
Hu
PI
Institution:
University
of Hawaii
The
majority of the most distant galaxies discovered to date have been found
by
strong Lyman alpha emission at red optical wavelengths.
An accurate
estimate
of the star formation rates for
these objects requires a measurement
of
the line-free UV continuum, which must be taken at infrared wavelengths.
Here
we propose to obtain imaging with NICMOS in the F160W filter for a
sample
of
9 Lyman alpha galaxies with redshifts z~6.5 up to z=6.740 from a
complete,
flux-limited
widefield narrowband and multi-color survey conducted on the 8-m
Subaru
Telescope. This program will investigate galaxy morphologies and star
formation
for a uniform sample of the highest redshift galaxies now known.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11109
Title:
Characterization
of the UV absorption feature in asteroid (1) Ceres
PI:
Jianyang
Li
PI
Institution:
University
of Maryland
We
propose to obtain the UV spectrum of asteroid (1) Ceres from 120 nm to
200
nm
with ACS/SBC objective prism to characterize the broad and deep
absorption
feature
within this wavelength range as reported recently.
Our scientific
goals
include, 1) to characterize the absorption band, 2) to determine the
origin
of this spectral feature and constrain the surface compositions of
Ceres,
and 3) to understand the albedo and color features on Ceres. HST is
the
only observatory currently capable of obtaining spectroscopy in this
wavelength
range. This observation will help
improve our knowledge about this
largest
and oldest asteroid, and support the planning of the upcoming NASA
Discovery
Program mission, Dawn, orbiting asteroids Vesta and Ceres.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM IN EXTERNAL GALAXIES
ID:
11110
Title:
Searching
for Lyman alpha Emission from FUSE Lyman Continuum Candidates
PI:
Stephan
McCandliss
PI
Institution:
The
Johns Hopkins University
We
have recently been granted time on FUSE to characterize the escape
fraction
of
hydrogen Lyman continuum (Lyc) photons from a morphologically diverse
set
of
star forming galaxies. The FUSE
program is designed to provide ~ 5 sigma
detections
of Lyc photons emitted from star
forming galaxies with escape
fractions
~5%. With this proposal we seek
hydrogen Lyman alpha (Lya)
observations
of a representative subset of the FUSE program targets to
constrain
the observational relationship between Lyc, Lya, and hydrogen Balmer
line
emission in these systems. Such
observations explore the detailed
balance
between the simple optically thin (Case A) and optically thick (Case
B)
limits in recombination theory.
The ultimate goal of this program is to
quantify
the relationship between escaping Lya and Lyc emission and the first
structures
that form in the early universe.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11111
Title:
A
Search for an Intermediate Mass Black Hole in the Globular Cluster NGC
6266
PI:
Bernard
McNamara
PI
Institution:
New
Mexico State University
We
propose to search for an intermediate mass black hole (IMBH) in the
core of
the
galactic globular cluster NGC 6266. Based on a comparison between the
observed
central surface brightness profiles of 38 globular clusters and
state-of-the
art N-body simultations, NGC 6266 offers the best hope of
detecting
an IMBH among these objects. This detection would be significnat for
at
least two reasons. It would be the first concrete discovery of an IMBH,
revealing
unique information about the environment in which these objects
form,
and second, its discovery would provide a powerful validation on the N-
body
simultations used to track the dynamical evolution of globular clusters.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11112
Title:
The
Collisional Ring Galaxy NGC922
PI:
Gerhardt
Meurer
PI
Institution:
The
Johns Hopkins University
We
request WFPC2 images of the newly recognized collisional ring galaxy
NGC922
which
will become the nearest such system observed by HST. These will be used
to
get a clear understanding of the geometry of the interaction and the
induced
star formation in this system.
Quantitive modeling of the colors of
the
star clusters and stellar populations will be used to constrain the star
formation
history of the system. They will
also be used to test the "infant
mortality"
scenario for star cluster evolution. The derived population ages
will
test predictions of how star formation evolves in the various components
(ring,
core, spokes) of collisional rings, and will improve our own
simulations
of this system. These will be used
to determine the final fate of
the
stars formed in the present burst - some will end up in a central bar or
bulge
while others will become part of a thickened disk.
By analogy this will
tell
us how similar collisions enrich stellar populations in the early
universe. This is especially relevant since the
number density of collisional
rings
increases rapidly with redshift.
======================================================================
Proposal
Category: SNAP
Scientific
Category: SOLAR SYSTEM
ID:
11113
Title:
Binaries
in the Kuiper Belt:
Probes
of Solar System Formation and Evolution
PI:
Keith
Noll
PI
Institution:
Space
Telescope Science Institute
The
discovery of binaries in the Kuiper Belt and related small body
populations
is powering a revolutionary step forward in the study of this
remote
region. Three quarters of the
known binaries in the Kuiper Belt have
been
discovered with HST, most by our snapshot surveys.
The statistics
derived
from this work are beginning to yield surprising and unexpected
results. We have found a strong concentration of
binaries among low-
inclination
Classicals, a possible size cutoff to binaries among the Centaurs,
an
apparent preference for nearly equal mass binaries, and a strong
increase
in
the number of binaries at small separations. We
propose to continue this
successful
program in Cycle 16; we expect to discover at least 13 new binary
systems,
targeted to subgroups where these discoveries can have the greatest
impact.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11114
Title:
Improving
proper motion measurements of the
stars in the field of SN 1572 with WFPC2
PI:
Pilar
Ruiz-Lapuente
PI
Institution:
Universidad
de Barcelona
We
propose to complete the spatial velocity measurements of the stars in
the
central
region of the remnant of SN 1572, one of the historical Galactic Type
Ia
supernovae. A new visit with WFPC2 would allow us to significantly
improve
the
accuracy of the proper motion measurements of the stars in the field,
since
we would benefit from a long temporal baseline by using the WFPC2 images
previously
taken. This unique legacy would complement the high-precision
ground-based
observations made for the stars in the SN 1572 field during the
past
ten years. The search for the companion star of Galactic Type Ia
supernovae,
based on their high peculiar velocity as a salient feature, has
already
pointed to a good candidate for SN 1572. The current uncertainties in
the
tangential velocity of the candidate star and the other stars in the
field
can
be reduced to less than a half with a visit in Cycle 16. This would lead
to
a precise determination of the parameters of the binary system that gave
rise
to the supernova. If not done during Cycle 16, the long temporal
baseline
for
SN 1572 with WFPC2 would be lost.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11115
Title:
Photometric
Imaging of Asteroid 2 Pallas
PI:
Christopher
Russell
PI
Institution:
University
of California - Los Angeles
We
propose to conduct the first HST imaging of Asteroid 2 Pallas with
WFPC2-PC
over
8 HST orbits. We will image the
asteroid in five filters: F336w,
F439w,
F555w,
F675w and F814w. We will utilize
these observations to drastically
improve
the knowledge of Pallas' shape, spin pole position and surface
properties,
including roughness and albedo, parameters that are poorly
determined
by previous study. These observations will result in high signal-
to-noise,
high resolution surface maps from the visible to the UV.
A
satellite
search will also be conducted for objects within the stability field
of
up to 21st magnitude, or about 900m in diameter. It
is demonstrated in our
proposal
that significant scientific opportunity exists in Cycle 16 because
Pallas
is at both a low-phase, 3.9 degree opposition and near its closest
approach
to Earth, conditions that do not occur simultaneously in the next
twenty
years. This window represents the
best chance to answer long standing,
fundamental
questions about Pallas, the main asteroid belt, and the formation
of
the solar system.
======================================================================
Proposal
Category: GO
Scientific
Category: COOL STARS
ID:
11116
Title:
Exploring
the Early FUV History of Cool Stars: Transition Regions at 30 Myr
PI:
Steven
Saar
PI
Institution:
Smithsonian
Institution Astrophysical Observatory
Stellar
magnetic activity derives from the so-called "dynamo," a
hydromagnetic
interplay
between overturning plasma motions and differential rotation in
stars
cool enough to support significant surface convection zones. The
magnetic
fields resulting from dynamo action are in turn are responsible for a
wide
range of high-energy emissions, including the spectacular outbursts
called
flares. Dynamo powered magnetic
activity is not confined solely to
stars,
but also must occur, for example, in accretion disks of all
descriptions,
and in some planets. A great deal
is known about magnetic
activity
in middle-aged G dwarfs like our Sun, thanks to its proximity. Less
is
known, however, about the much younger stars, newly emerged from the T-
Tauri
stage. Yet, it is during this
phase that they reach the peak of their
magnetic
activity, and subsidiary influences, such as the impact of ionizing
radiation
and strong coronal winds on developing solar systems, also are
maximum. One of the key missing ingredients in
our current understanding are
measurements
of FUV emissions of such stars, to complement the extensive
collections
of coronal (1-10 MK) X-ray measurements, particularly from recent
ROSAT,
Chandra and XMM-Newton surveys. We
propose to conduct sensitive
ACS/SBC
prism ultraviolet spectroscopy of selected fields in two young (30
Myr)
Galactic clusters--IC 2391 and IC 2602--to inventory the key C IV
emission
index (~0.1 MK) over a much larger and more diverse sample of coeval
objects
than has been possible hitherto. A
key question is whether the FUV
emissions
also suffer the "saturation" and "super-saturation" at
short
rotation
periods seen in coronal X-rays, or whether they continue to rise in
the
fastest rotating stars. The
saturation behavior of the different
temperature
regimes holds important clues to the organization of the surface
active
regions on these very young stars, and should allow us to distinguish
among
several competing models.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11117
Title:
The
Search for Atmospheric Water in the Transiting Planet HD189733b
PI:
David
Sing
PI
Institution:
CNRS,
Institut d'Astrophysique de Paris
We
propose to use the NICMOS camera to search for transit NIR signatures of
atmospheric
water in HD189733b. While water
absorption bands exist in the
optical
and IR, space-based NIR signatures are uniquely positioned to offer
the
best chance at detection. Using
narrow band photometric filters, we will
be
able to detect absorption signatures while the planet is in primary
transit. A positive detection would be the first
proof of water on an
extrasolar
planet. Furthermore, it would
provide invaluable planetary
information,
constraining the entire chemistry.
As a byproduct of the high
SNR
required for our primary science goal, we will be able to improve on the
value
of the planetary radius, a result independent of our primary science
objective. The accurate radius estimate, together
with planet structure
models,
will allow constraining the planet interior and its relationship with
formation
models and stellar metallicity.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11118
Title:
Investigating
Near-Equinox Atmospheric Change on Uranus
PI:
Lawrence
Sromovsky
PI
Institution:
University
of Wisconsin - Madison
Uranus
is approaching its 7 December 2007 equinox, when we will be able to
observe
the entire northern hemisphere for the first time with modern cameras.
The
large seasonal phase shift expected from its long radiative time
constant
implies
that it should now exhibit nearly maximal hemispheric contrast, and
should
be in the process of reversing.
Many changes already observed, such as
the
development of the first visible-wavelength dark spot, discovered in
Cycle
15,
and the fading of the south polar cap may be indicative of the expected
reversal. We propose a detailed characterization
of Uranus' current seasonal
response
with a 7-orbit program consisting of 1 orbit of NICMOS imaging of
cloud
bands and 6 orbits of WFPC2 imaging using both broadband and narrow-band
filters
capable of tracking dark and bright discrete cloud features. Filters
between
0.467 and 1.87 microns will provide vertical sensing depths scanning
through
the pressure range where the putative methane and deeper H2S clouds
might
plausibly exist and provide strong constraints on their contributions
and
parent gas mixing ratios. These
observations have unique combinations of
spectral
range and resolution with needed temporal and spatial resolution not
available
from groundbased observations. Only HST is capable of investigating
the
Uranus dark spot.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11119
Title:
The
Stellar Origins of Supernovae
PI:
Schuyler
Van Dyk
PI
Institution:
Jet
Propulsion Laboratory
Supernovae
(SNe) have a profound effect on galaxies, and have been used
recently
as precise cosmological probes, resulting in the discovery of the
accelerating
Universe. They are clearly very
important events deserving of
intense
study. Yet, even with nearly 4000
known SNe, we know relatively
little
about the stars which give rise to these powerful explosions. The main
limitation
has been the lack of spatial resolution in pre-SN imaging data.
However,
since 1999 our team has been at the vanguard of directly identifying
SN
progenitor stars in HST images.
From this exciting new line of study, the
emerging
trend from 5 detections for Type II-Plateau SNe is that their
progenitors
appear to be relatively low mass (8 to 20 Msun) red supergiants,
although
more cases are needed.
Nonetheless, the nature of the progenitors of
Type
Ib/c SNe, a subset of which are associated with the amazing gamma-ray
bursts,
remains ambiguous. Furthermore, we
remain in the continually
embarrassing
situation that we still do not yet know which progenitor systems
explode
as Type Ia SNe, which are currently being used for precision
cosmology. We propose to confirm the identities of
the progenitors of 4 SNe
within
17 Mpc, which we expect to occur during Cycle 16, through ToO
observations
using WFPC2/PC.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11120
Title:
A
Paschen-Alpha Study of Massive Stars and the ISM in the Galactic Center
PI:
Daniel
Wang
PI
Institution:
University
of Massachusetts
The
Galactic center (GC) is a unique site for a detailed study of a
multitude
of
complex astrophysical phenomena, which may be common to nuclear regions
of
many
galaxies. Observable at resolutions unapproachable in other galaxies,
the
GC
provides an unparalleled opportunity to improve our understanding of the
interrelationships
of massive stars, young stellar clusters, warm and hot
ionized
gases, molecular clouds, large scale magnetic fields, and black holes.
We
propose the first large-scale hydrogen Paschen alpha line survey of the
GC
using
NICMOS on the Hubble Space Telescope. This survey will lead to a high
resolution
and high sensitivity map of the Paschen alpha line emission in
addition
to a map of foreground extinction, made by comparing Paschen alpha to
radio
emission. This survey of the inner 75 pc of the Galaxy will provide an
unprecedented
and complete search for sites of massive star formation. In
particular,
we will be able to (1) uncover the distribution of young massive
stars
in this region, (2) locate the surfaces of adjacent molecular clouds,
(3)
determine important physical parameters of the ionized gas, (4) identify
compact
and ultra-compact HII regions throughout the GC. When combined with
existing
Chandra and Spitzer surveys as well as a wealth of other multi-
wavelength
observations, the results will allow us to address such questions
as
where and how massive stars form, how stellar clusters are disrupted,
how
massive
stars shape and heat the surrounding medium, and how various phases of
this
medium are interspersed.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11121
Title:
Proper
Motion of the Remarkable Irradiated Jet HH399 in the Trifid Nebula
PI:
Farhad
Yusef-Zadeh
PI
Institution:
Northwestern
University
The
Trifid nebula has recently been of much interest because of its
identification
with a large number of massive protostars, as well as young
stellar
objects. HH 399 is one of the most spectacular Herbig-Haro flows
recognized
to be irradiated by the UV flux of the massive O7.5 star in the
Trifid
nebula. The irradiated jet, which is propagating in a fully ionized
medium,
contains numerous knots along the jet and also shows evidence for a
number
of isolated knots running immediately outside the jet. Two different
HST
observations of the nebula, with different scientific goals, were
carried
out
in 1997 and 2002, having sensitivities that differed by a factor of 10.
We
performed
preliminary proper motion measurements of the jet based on these
observations
and discovered a continuous velocity structure of the bright
knots
of about 230 km/sec. Here we propose four WFPC2 orbits to reobserve HH
399
in order to carry out accurate proper motion measurements over the full
extent
of the jet, based on observations spanning more than 10 years and
having
equally deep sensitivity. The proposed observations are not simply a
repeat
of previous measurements, as this will be the first highly accurate
proper
motion measurement of an irradiated jet based on two identical epochs
of
WFPC2 observations. The observations will improve the accuracy of proper
motion
measurements for HH 399 by more than a factor of five and will address
important
questions beyond our preliminary result. Currently measured velocity
differences
between the jet features are barely significant. The factor of 5
increase
in accuracy will establish the evidence for deceleration along the
jet
and the lateral motion of the jet. In addition, these measurements will
address
the kinematics of individual entrained and isolated blobs of the jet
as
it propagates into an HII region associated with the nebula. This is the
last
opportunity to perform this experiment before WFPC2 is removed from HST.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11122
Title:
Expanding
PNe: Distances and Hydro Models
PI:
Bruce
Balick
PI
Institution:
University
of Washington
We
propose to obtain repeat narrowband images of a sample of eighteen
planetary
nebulae (PNe) which have HST/WFPC2 archival data spanning time
baselines
of a decade. All of these targets
have previous high signal-to-
noise
WFPC2/PC observations and are sufficiently nearby to have readily
detectable
expansion signatures after a few years.
Our main scientific
objectives
are (a) to determine precise distances to these PNe based on their
angular
expansions, (b) to test detailed and highly successful hydrodynamic
models
that predict nebular morphologies and expansions for subsamples of
round/elliptical
and axisymmetric PNe, and (c) to monitor the proper motions
of
nebular microstructures in an effort to learn more about their physical
nature
and formation mechanisms. The proposed
observations will result in
high-precision
distances to a healthy subsample of PNe, and from this their
expansion
ages, luminosities, CSPN properties, and masses of their ionized
cores. With good distances and our hydro
models, we will be able to determine
fundamental
parameters (such as nebular and central star masses, luminosity,
age). The same images allow us to monitor the
changing overall ionization
state
and to search for the surprisingly non-homologous growth patterns to
bright
elliptical PNe of the same sort seen by Balick & Hajian (2004) in
NGC
6543. Non-uniform growth is a sure sign of
active pressure imbalances within
the
nebula that require careful hydro models to understand.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11123
Title:
A
NICMOS Survey for Proplyds in the RCW 38 Massive Embedded Cluster
PI:
Tyler
Bourke
PI
Institution:
Smithsonian
Institution Astrophysical Observatory
We
propose a search for line emission from photoevaporating protoplanetary
disks
in the Massive Embedded Cluster
RCW 38. These disks would be analogous
to
the "proplyds" discovered in the Orion Nebula:
disks around young low
mass
stars
which are being photoionized by a nearby O star. We
will search for
these
disks in RCW 38 using narrowband imaging in the lines of Paschen alpha
and
molecular hydrogen (1-0) S(1) with NICMOS. The
RCW 38 region is an
excellent
target for determining whether proplyds are observable
in large
numbers
outside of Orion. It is a young
embedded cluster hosting a few
hundred
low mass young stars with a large percentage showing infrared excess
indicating
the presence of disks. About 100
of these stars are found within
0.1
pc of the central O5 star, and the cluster is located within a cleared
cavity
0.2 pc in size, embedded within a
molecular cloud, exposing the
cluster
members directly to the UV radiation from the O star.
Unlike Orion,
but
like many other young clusters, RCW 38 is not seen in visible light, and
infrared
imaging is needed. The best line
in the infrared for revealing
proplyds
is the Paschen alpha line, which is not detectable from the ground.
Only
HST is able to perform these observations. From
these observations we
will
estimate the lifetime of the evaporating disks, and ascertain whether
these
disks will survive long enough to form planets.
======================================================================
Proposal
Category: GO
Scientific
Category: QUASAR ABSORPTION LINES AND IGM
ID:
11124
Title:
The
Origin of QSO Absorption Lines from QSOs
PI:
David
Bowen
PI
Institution:
Princeton
University
We
propose using WFPC2 to image the fields of 10 redshift z ~ 0.7
foreground
(FG)
QSOs which lie within ~29-151 kpc of the sightlines to high-z background
(BG)
QSOs. A surprisingly high fraction of the BG QSO spectra show strong
MgII
(2796,2803)
absorption lines at precisely the same redshifts as the FG QSOs.
The
high resolution capabilities of WFPC2 are needed to understand the
origin
of
these absorption systems, in two ways.
First, we wish to explore the FG
QSO
environment as close as possible to the position of the BG QSO, to
search
for
interloping group or cluster galaxies which might be responsible for the
absorption,
or irregularly shaped post-merger debris between the FG and BG QSO
which
may indicate the presence of large amount of disrupted gas along a
sightline.
Similarly, high resolution images are needed to search for signs of
tidal
interactions between any galaxies which might be found close to the FG
QSO.
Such features might provide evidence of young merging events causing the
start
of QSO duty cycles and producing outflows from the central AGN. Such
winds
may be responsible for the observed absorption lines.
Second, we seek
to
measure the intrinsic parameters of the FG QSO host galaxy, such as
luminosity
and morphology, to correlate with the properties of the MgII
absorption
lines. We wish to observe each
field through the F814W filter,
close
to the rest-frame B-band of the FG QSO. These blue data can reveal
enhanced
star formation regions close to the nucleus of the host galaxy, which
may
be indicative of galaxy mergers with the FG QSO host. The FG QSO
environment
offers quite a different set of phenomena which might be
responsible
for MgII absorption, providing an important comparison to studies
of
MgII absorption from regular field galaxies.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11125
Title:
The
Dynamical Evolution of Globular Clusters
PI:
Joel
Bregman
PI
Institution:
University
of Michigan
Globular
clusters evolve through dynamical interactions, with primordial
binaries
extending the time until core collapse by up to an order of
magnitude,
depending on the initial binary fraction.
These dynamical
interactions
plus mass segregation causes the binary fraction to rise in the
core
but fall at larger radii. We hope
to eventually test these broad
predictions
by comparing them to the binary properties for globular clusters
at
different states of evolution, defined by the ratio of their age to the
dynamical
relaxation time at the half-light radius.
The most important
unknown
aspects in the modeling process are the initial conditions of binaries
in
the cluster. Here we propose to
determine the initial binary fraction as a
function
of radius by studying three of the dynamically youngest globular
clusters
(NGC 5053, NGC 5466, and NGC 5897).
The presence of binaries
thickens
the Main Sequence in a color-magnitude diagram, which can be detected
with
deep multicolor images.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11126
Title:
Resolving
the Smallest Galaxies
PI:
Kristin
Chiboucas
PI
Institution:
University
of Hawaii
An
order of magnitude more dwarf galaxies are expected to inhabit the Local
Group,
based on currently accepted galaxy formation models, than have been
observed. This discrepancy has been noted in
environments ranging from the
field
to rich clusters, with evidence emerging that lower density regions
contain
fewer dwarfs per giant than higher density regions, in further
contrast
to model predictions. One possible
explanation for this involves the
effects
of reionization on the forming galaxies and naturally explains both
the
dearth of dwarf galaxies and the apparent environmental dependence.
However,
before such theories can be fully tested, we require a better
understanding
of the distribution of dwarf galaxies. Currently, there is no
complete
census of the faintest dwarf galaxies in any environment.
The
discovery
of the smallest and faintest dwarfs is hampered by the limitations
in
detecting such faint and low surface brightness galaxies, and this is
compounded
by the great difficulty in determining accurate distances to, or
ascertaining
group membership for, such faint objects.
The M81 group provides
a
unique means for establishing membership for galaxies in a low density
region
complete to magnitudes as faint as M_R ~ -7. With
a distance modulus
of
27.8, the tip of the red giant branch (TRGB) appears at I ~ 24, just
within
the
reach of ground based surveys. We
currently have surveyed a 30 square
degree
region around M81 with the CFHT/Megacam.
From these images we have
detected
15 new candidate dwarf galaxies.
We propose to use the HST with
WFPC2
to image these 15 galaxies in F606W and F814W bands in order to
construct
a color-magnitude diagram down to I = 25.5 from which to measure
accurate
TRGB distances to these candidate galaxies and determine star
formation
and metallicity histories. The
overall project will provide a
survey
of the dwarf galaxies in the M81 group environment with unprecedented
completeness
to a limit of M_R < -7.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11127
Title:
Mapping
the nebula surrounding the enigmatic X-ray source at the center of the
Vela Jr
SNR
PI:
Andrea
De Luca
PI
Institution:
CNR,
Istituto di Astrofisica Spaziale
A
compact X-ray source, showing nothing but steady unpulsed thermal
emission,
lies
close to the center of the young and nearby supernova remnant dubbed
"Vela
Jr". It is a typical member of a class of enigmatic sources, supposed to
be
the youngest members of the radio-quiet neutron star family. Quite
surprisingly,
we discovered in ground-based optical observations a small
Halpha
nebula spatially coincident with the X-ray source. Such a nebula
potentially
carries very important information on the nature of the X-ray
source,
which remains elusive in spite of large observational efforts. We
propose
to use the WFPC2 to collect high
resolution Halpha images of the
nebula
in order to resolve its structure, to understand its nature, and to
identify
its connection with the X-ray source. Addressing all these points
will
also have important implications for our interpretation of the compact
X-
ray
source and on of other objects of the same class.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11128
Title:
Time
Scales Of Bulge Formation In Nearby Galaxies
PI:
David
Fisher
PI
Institution:
University
of Texas at Austin
Traditionally,
bulges are thought to fit well into galaxy formation models of
hierarchical
merging. However, it is now becoming well established that many
bulges
formed through internal, secular evolution of the disk rather than
through
mergers. We call these objects pseudobulges. Much
is still unknown
about
pseudobulges, the most pressing questions being:
How, exactly, do they
build
up their mass? How long does it take? And, how many exist?
We are after
an
answer to these questions. If pseudobulges form and evolve over longer
periods
than the time between mergers, then a significant population of
pseudobulges
is hard to explain within current galaxy formation theories. A
pseudobulge
indicates that a galaxy has most likely not undergone a major
merger
since the formation of the disk. The ages of pseudobulges give us an
estimate
for the time scale of this quiescent evolution. We propose to use
21.4
orbits of HST time to complete UBVIH imaging on a sample of 33 nearby
galaxies
that we have observed with Spitzer in the mid-IR. These data will be
used
to measure spatially resolved stellar population parameters (mean
stellar
age,
metallicity, and star formation history); comparing ages to star
formation
rates allows us to accurately constrain the time scale of
pseudobulge
formation. Our sample of bulges
includes both pseudo- and
classical
bulges, and evenly samples barred and unbarred galaxies. Most of our
sample
is imaged, 13 have complete UBVIH coverage; we merely ask to complete
missing
observations so that we may construct a uniform sample for studying
bulge
formation. We also wish to compare
the stellar population parameters to
a
variety of bulge and global galaxy properties including star formation
rates,
dynamics, internal bulge morphology, structure from bulge-disk
decompositions,
and gas content. Much of this data set is already or is being
assembled.
This will allow us to derive methods of pseudobulge identification
that
can be used to accurately count pseudobulges in large surveys. Aside
from
our
own science goals, we will present this broad set of data to the
community. Thus, we waive proprietary periods for
all observations.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11129
Title:
The
Star Formation History of the Fornax Dwarf Spheroidal Galaxy
PI:
Enrico
Held
PI
Institution:
Osservatorio
Astronomico di Padova
The
Fornax dwarf spheroidal galaxy is one of the most luminous dwarf
satellites
of the Milky Way. It is unusual in
many ways:
it
hosts 5 globular
clusters,
shows some relatively young stars, and has faint sub-structures
which
have been interpreted as signs of recent interactions.
It is thus of
great
interest to learn the complete star formation history (SFH) of Fornax to
establish
a link between its evolutionary path and the predictions from
numerical
simulations, as a test of our understanding of dwarf galaxy
evolution.
Yet many questions remain open. Is
the old stellar population made
up
of stars formed in a very early burst, perhaps before the epoch of
reionisation,
or the result of a more continuous star formation between 13 and
9
Gyr ago ? How quickly did Fornax increase its metallicity during its
initial
assembly
and during subsequent episodes of star formation ?
Are accretion
episodes
required to explain the age-metallicity history of Fornax ? However,
there
has never been a comprehensive study of the global SFH of the Fornax
field
based on data of sufficient depth to unambiguously measure the age
mixture
of the stellar populations and their spatial variation. We propose to
use
the WFPC2 to obtain very deep images in several fields across the
central
region
of Fornax in order to reach the oldest main-sequence turnoffs. The
number
of fields is determined by the need to measure the SFH over different
regions
with distinct kinematics and metallicity.
The resolution achievable
with
HST is crucial to answer these questions because, to derive the age
distribution
of the oldest stars, we are interested in I magnitude differences
of
the order 0.2 mag in crowded fields at V=24.5. We
will directly measure
the
time variation in star-formation rate over the entire galaxy history,
from
first
stars coeval with the Milky Way halo to the youngest populations 200 Myr
ago.
The combination of detailed CMD analysis with WFPC2 with our existing
metallicity
and kinematic information will allow us to trace out the early
phases
of its evolution.
======================================================================
Proposal
Category: GO
Scientific
Category: AGN/QUASARS
ID:
11130
Title:
AGNs
with Intermediate-mass Black Holes: Testing the Black Hole-Bulge
Paradigm, Part
II
PI:
Luis
Ho
PI
Institution:
Carnegie
Institution of Washington
The
recent progress in the study of central black holes in galactic nuclei
has
led
to a general consensus that supermassive (10^6-10^9 solar mass) black
holes
are closely connected with the formation and evolutionary history of
large
galaxies, especially their bulge component. Two
outstanding issues,
however,
remain unresolved. Can central
black holes form in the absence of a
bulge? And does the mass function of central
black holes extend below 10^6
solar
masses? Intermediate-mass black
holes (<10^6 solar masses), if they
exist,
may offer important clues to the nature of the seeds of supermassive
black
holes. Using the SDSS, our group
has successfully uncovered a new
population
of AGNs with intermediate-mass black holes that reside in low-
luminosity
galaxies. However, very little is
known about the detailed
morphologies
or structural parameters of the host galaxies themselves,
including
the crucial question of whether they have bulges or not.
Surprisingly,
the majority of the targets of our Cycle 14 pilot program have
structural
properties similar to dwarf elliptical galaxies. The
statistics
from
this initial study, however, are really too sparse to reach definitive
conclusions
on this important new class of black holes. We
wish to extend
this
study to a larger sample, by using the Survey mode to obtain WFPC2 F814W
images
of 85 (from a parent sample of 175) AGNs with intermediate-mass black
holes
selected from our final SDSS search.
We are particularly keen to
determine
whether the hosts contain bulges, and if so, how the fundamental
plane
properties of the host depend on the mass of their central black holes.
We
will also investigate the environment of this unique class of AGNs.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM IN EXTERNAL GALAXIES
ID:
11131
Title:
Star
formation at large radii in cooling flow brightest cluster galaxies
PI:
Walter
Jaffe
PI
Institution:
Sterrewacht
Leiden
We
propose to take deep ACS FUV images of the bright central galaxies in
two
powerful
cooling flow clusters for which we have VLT UBR images, with the
object
of determining whether the UV excesses we observe at large radii
(>15kpc)
are caused by young stars, ultrahot (WR) stars, or an as yet unknown
source. Current models of excess UV light at
the AGN-dominated centers of
these
galaxies cannot easily be extended to large radii.
New understanding of
star
formation in these clusters will be directly applicable to scenarios of
galaxy
formation in the early universe.
======================================================================
Proposal
Category: GO
Scientific
Category: COOL STARS
ID:
11132
Title:
Constraining
the age of the AB Dor system
PI:
Markus
Janson
PI
Institution:
Max-Planck-Institut
fur Astronomie, Heidelberg
The
zero-age main sequence K-type star AB Dor, with an age of 25 to 125 Myr,
is
the most active young star in the solar neighbourhood. It is part of a
quadruple
system of young stars. The mass of AB Dor C, the
closest and lowest
mass
companion, has been derived from
astrometric observations (with the VLA
and
adaptive optics at the VLT) to
94+-3 times the mass of Jupiter. The low
mass
(close to the hydrogen burning limit) combined with the young age makes
AB
Dor C a unique calibration source for evolutionary tracks for very
low-mass
stars
and brown dwarfs, provided that a precise age estimate can be derived
for
the system. We propose to use the HST planetary camera to obtain
resolved
component
photometry of the M-type pre-main sequence star AB Dor Ba
and Bb in
order
to derive individual spectral types and luminosities, which will enable
us
to age-date the AB Dor system to better than +-20 Myr. In addition, the
observations
will help to constrain the Ba/Bb orbit, and hence to derive
dynamical
mass estimates as well.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11133
Title:
Late-Time
Photometry of SN 2005hk: A New Kind of Type Ia Supernova
PI:
Saurabh
Jha
PI
Institution:
Rutgers
the State University of New Jersey
Our
lack of understanding of Type Ia supernova (SN Ia) explosions limits our
confidence
in their use for cosmology. While
there is broad agreement that
these
objects represent the explosions of white dwarfs, the details of the
explosion
mechanism are not well-understood.
Recent observations have
detected
a previously unacknowledged variant class of SNe Ia whose photometric
and
spectroscopic peculiarities make them quite distinct from normal SNe Ia.
These
objects represent a challenge for thermonuclear supernova models, as a
complete
theory of exploding white dwarfs must allow for their existence. A
particularly
well-studied example of this class of objects is the recent SN
2005hk,
whose properties in some respects resemble those of models which
invoke
a subsonic burning front, called a deflagration. We
propose to test SN
Ia
models by obtaining late-time photometry for this extreme SN Ia using
WFPC2
and
NICMOS on HST. We will accurately
measure the late-time photometric
decline
rate and spectral energy distribution (SED). These
observations will
allow
us to test whether the ejecta contain the large amount of oxygen
predicted
by certain models, the efficiency of energy deposition by gamma rays
and
positrons, and possibly detect major evolution of the SED expected due
to
a
change in the dominant cooling mechanism of the ejecta.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11134
Title:
WFPC2
Tidal Tail Survey: Probing Star
Cluster Formation on the Edge
PI:
Karen
Knierman
PI
Institution:
University
of Arizona
The
spectacular HST images of the interiors of merging galaxies such as the
Antennae
and NGC 7252 have revealed rich and diverse populations of star
clusters
created over the course of the interaction. Intriguingly,
our WFPC2
study
of tidal tails in these and other interacting pairs has shown that star
cluster
birth in the tails does not follow a similarly straightforward
evolution. In fact, cluster formation in these
relatively sparse environments
is
not guaranteed -- only one of six tails in our initial study showed
evidence
for a significant population of young star clusters.
The tail
environment
thus offers the opportunity to probe star cluster formation on the
edge
of the physical parameter space (e.g., of stellar and gas mass, density,
and
pressure) that permits it to occur.
We propose to signficantly extend our
pilot
sample of optically bright, gas-rich tidal tails by a factor of 4 in
number
to include a more diverse population of tails, encompassing major and
minor
mergers, gas-rich and gas-poor tails, as well as early, late, and merged
interaction
stages. With 21 orbits of HST WFPC2 imaging in the F606W and F814W
filters,
we can identify, roughly age-date, and measure sizes of star clusters
to
determine what physical parameters affect star cluster formation. WFPC2
imaging
has been used effectively in our initial study of four mergers, and it
will
be possible in this program to reach similar limits of Mv=-8.5 for each
of
16 more tails. With the much
larger sample we expect to isolate which
factors,
such as merger stage, HI content, and merger mass ratio, drive the
formation
of star clusters.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11135
Title:
Extreme
makeovers: Tracing the transformation of massive galaxies at z~2.5
PI:
Mariska
Kriek
PI
Institution:
Universiteit
Leiden
To
obtain a full spectroscopic census of the universe at z~2.5 we have
conducted
a near-infrared spectroscopic survey for K-selected galaxies. We
found
that, in contrast to the local universe, massive high-redshift galaxies
span
a wide range of properties, varying from (dusty) star burst to "red and
dead"
galaxies. This may imply that massive galaxies transform from star-
forming
to quiescent galaxies in the targeted redshift range. To understand
whether
the 9 quiescent galaxies in our sample are the progenitors of local
elliptical,
we are observing them in the current cycle with NIC2.
For cycle
16
we propose to complete our sample of massive z~2.5 galaxies and image
the
remaining
10 galaxies, which all have emission lines. Based on emission-line
diagnostics,
6 of these galaxies are identified as star-forming objects and 4
harbor
an active galactic nucleus. The goals are to 1) determine whether star
formation
in massive z~2.5 galaxies takes place in disks or is triggered by
merger
activity, 2) derive the contribution of AGNs to the rest-frame optical
emission,
and 3) test whether the morphologies are consistent with the idea
that
the star-forming galaxies, AGNs, and quiescent galaxies represent
subsequent
phases of an evolutionary sequence. The combination of both
programs
will provide the first morphological study of a spectroscopically
confirmed
massive galaxy sample at z~2.5.
======================================================================
Proposal
Category: GO
Scientific
Category: COOL STARS
ID:
11136
Title:
Resolving
Ultracool Astrophysics with Brown Dwarf Binaries
PI:
Michael
Liu
PI
Institution:
University
of Hawaii
We
propose to obtain resolved far-red and near-IR photometry of 14 brown
dwarf
binaries
with HST/NICMOS in order to study one of the long-standing puzzles in
ultracool
astrophysics, namely the rapid change in spectra from L dwarfs to T
dwarfs
at nearly constant effective temperature (a.k.a. the ``L/T
transition''). While many nearby brown dwarfs have
been studied, use of such
samples
is inevitably hindered by the unknown ages, masses, and metallicities
of
the field population.
Characterization of resolved ultracool binaries is a
promising
avenue for addressing this problem, by providing coeval systems of
the
same composition with comparable masses and temperatures.
Our proposed
HST/NICMOS
(0.9-1.6 micron) observations will be combined with longer
wavelength
ground-based photometry and spectroscopy from Keck laser guide star
adaptive
optics. The resulting multi-band
(0.9-2.5 micron) dataset will be a
unique
resource for measuring the evolution of spectral energy distributions
across
the L/T transition, to test state-of-the-art atmospheric models, and to
determine
the physical process(es) that dominate the L/T transition.
Understanding
the L/T transition is important not only for testing brown dwarf
atmospheres,
but also provides a key pathway for understanding the same
physical
effects, namely the formation and removal of clouds, in the
atmospheres
of the extrasolar planets.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11137
Title:
First
Accurate Geometric Distance to a Galactic Wolf-Rayet Star: Knots in the
Ejecta
M1-67
PI:
Anthony
Moffat
PI
Institution:
Universite
de Montreal
M
1-67 is the youngest known ejection nebula surrounding a Population I
Wolf-
Rayet
star, in this case the WN8 star WR 124.
Our deep H-alpha HST/WFPC2
image
of this object in March 1997 revealed, for the first time in such a
nebula,
numerous bright, mostly unresolved knots (typical diameters 0.1-0.2")
often
surrounded by what appear to be their own local spherical diffuse 'wind'
bubbles.
We propose to obtain a second epoch H-alpha image of M 1-67,
essentially
repeating the Epoch1 instrumental set-up. By measuring the proper
motions
of the knots, we will derive a
relatively precise and assumption-free
geometric
distance (thus also a luminosity)
to a Galactic Wolf-Rayet
star,
the
first of its kind. This will help to confirm the suspected runaway
status
of
WR 124 and shed new light on the nature of progenitors of
gamma-ray
bursts.
Moreover, we intend to document and measure the anticipated
morphology/brightness
changes in the fine-stucture features of the nebula over
the
11-year interval, as they relate to wind-embedded shocks. This will
provide
important input for interaction models of a stellar wind with
circumstellar
matter.
======================================================================
Proposal
Category: GO
Scientific
Category: AGN/QUASARS
ID:
11138
Title:
The
Physics of the Jets of Powerful Radio Galaxies and Quasars
PI:
Eric
Perlman
PI
Institution:
Florida
Institute of Technology
We
propose to obtain HST polarimetry of the jets of the quasars 1150+497
and
PKS
1136-135. Our goal is to solve the
riddle of their high-energy emission
mechanism,
and tackle issues such as particle acceleration and jet dynamics.
Our
targets are the optically brightest quasar jets, and they span the range
of
luminosities and beaming parameters seen in these objects.
Recent
observations
with Spitzer, HST and Chandra have shed new light on the spectral
morphology
of quasar jets, throwing wide open the question of the nature of
their
optical and X-ray emission. Three
mechanisms are possible, including
synchrotron
emission as well as two Comptonization processes. Polarimetry
can
uniquely
determine which of these mechanisms operates in the optical. We will
compare
the optical polarimetry to in-hand radio polarimetry as well as in-
hand
and new Spitzer, HST and Chandra imaging to gain new insights on the
structure
of these jets, as well as particle acceleration mechanisms and jet
dynamics.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11139
Title:
NICMOS
Observations of the Microquasar GRS 1758-258
PI:
Ian
Smith
PI
Institution:
Rice
University
The
galactic black hole candidate GRS 1758-258 is normally one of the
brightest
persistent gamma-ray sources in the vicinity of the galactic center.
It
is a microquasar with relativistic radio jets emanating from a central
variable
source. Microquasars are excellent
nearby test laboratories for
studying
the complex accretion and outflow processes that take place near
black
hole horizons. Despite an accurate
location provided by Chandra and the
VLA
and over a decade of careful ground-based studies, the optical/infrared
counterpart
to GRS 1758-258 remains unknown. A stellar counterpart is
expected,
but the current candidates are all more than 2 sigma from the center
of
the error circle. The ground-based
infrared flux limits are also right at
the
values expected for the synchrotron emission from the outflow from the
black
hole, and possibly for the emission from the accretion disk. This leaves
open
the question as to what is powering this very energetic persistent
source. Here we propose to use NICMOS to
perform broad-band imaging of the
GRS
1758-258 error box. These images
will be more than three magnitudes more
sensitive
than the current ground-based ones. The resulting spectra will
reveal
the thermal/non-thermal nature of the sources in the region of the
error
box, and the high spatial resolution images may reveal a jet structure.
We
propose to perform three visits of two orbits each spanning the
suggested
18.45
day binary orbital period of the system: a
correct counterpart
identification
should be confirmed by its variability.
We will also aim to
support
the HST observations with X- and gamma-ray observations using Swift or
INTEGRAL,
and with longer wavelength observations from the ground.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11140
Title:
Can
mass-ejections from late He-shell flash stars constrain
convective/reactive
flow modeling of stellar interiors?
PI:
Klaus
Werner
PI
Institution:
Universitat
Tubingen, Institut fur Astronomie & Astrophysik
The
existence of H-deficient knots around the central stars of the planetary
nebulae
Abell 30 and Abell 78 is still unexplained. We hypothesize that these
knots
were ejected during a very late helium-shell flash (= very late thermal
pulse,
VLTP) suffered by the precursor white dwarf stars. If this is true,
then
the characteristics of these knots (mass, velocity, density, spatial
distribution)
allow to draw conclusions on the course of the hydrogen-
ingestion
flash detonation that is triggered by the He-shell flash. This
provides
important, otherwise inaccessible constraints for the hydrodynamical
modeling
of convective/reactive flows in stellar interiors. Understanding the
physics
of these flows is not only important for the understanding of these
particular
central stars, but also for the frequent, very similar
convective/reactive
events that determine the nucleosynthesis in Pop. III
stars. With this proposal we want to proof or
discard the idea that the H-
deficient
knots are resulting from a VLTP. If true, then they can be exploited
for
flash-physics diagnostics. We propose a simple test. We search for such
knots
around five H-deficient central stars (PG1159 stars). Our models
predict,
that only those stars with residual nitrogen in the atmosphere have
suffered
a VLTP and, hence, should have expelled knots. We therefore want to
take
[O III] images of stars which have photospheric N and those which do
not.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11141
Title:
White
dwarfs in the open star cluster NGC 188
PI:
Kurtis
Williams
PI
Institution:
University
of Texas at Austin
White
dwarf cooling sequences represent the only ways in which we can
determine
ages of Galactic components such as the disk and the halo, and they
are
an independent check on main sequence ages of globular
star clusters.
These
age measurements rely heavily on theoretical cooling models, many of
which
disagree by as much as a few gigayears for the coolest white dwarfs.
Further,
observations of the white dwarf sequence in the super metal-rich open
cluster
NGC 6791 have found a white dwarf age several gigayears younger than
the
accepted cluster age determined by main-sequence fitting.
The white dwarf
sequence
of the solar-metallicity, 7-Gyr old open cluster NGC 188 can provide
some
much-needed insight into these uncertainties, but previous HST
observations
were too shallow to detect the oldest, faintest white dwarfs in
the
cluster. We propose deep imaging
of two fields at the center of the
cluster
with the following goals: (1)
To detect the end of the white dwarf
cooling
sequence, providing a much-needed empirical data point for cool white
dwarf
evolutionary models, (2) to compare the white dwarf luminosity function
of
NGC 188 with that of NGC 6791 to determine if the odd white dwarf
sequence
in
the latter cluster is due to the cluster's high metallicity or due to a
shortcoming
in theoretical models, and (3) to determine via photometry the
masses
of white dwarfs formed by solar-mass stars, a quantity not yet
empirically
measured.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM IN EXTERNAL GALAXIES
ID:
11142
Title:
Revealing
the Physical Nature of Infrared Luminous Galaxies at 0.3<z<2.7
Using HST
and Spitzer
PI:
Lin
Yan
PI
Institution:
California
Institute of Technology
We
aim to determine physical properties of IR luminous galaxies at
0.3<z<2.7
by
requesting coordinated HST/NIC2 and MIPS 70um observations of a unique,
24um
flux-limited sample with complete Spitzer mid-IR spectroscopy. The 150
sources
investigated in this program have S(24um) > 0.8mJy and their mid-IR
spectra
have already provided the majority targets with spectroscopic
redshifts
(0.3<z<2.7). The proposed 150~orbits of NIC2 and 66~hours of MIPS
70um
will provide the physical measurements of the light distribution at the
rest-frame
~8000A and better estimates of the bolometric luminosity. Combining
these
parameters together with the rich suite of spectral diagnostics from the
mid-IR
spectra, we will (1) measure how common mergers are among LIRGs and
ULIRGs
at 0.3<z<2.7, and establish if major mergers are the drivers of
z>1
ULIRGs,
as in the local Universe. (2) study the co-evolution of star formation
and
blackhole accretion by investigating the relations between the fraction
of
starburst/AGN
measured from mid-IR spectra vs. HST morphologies, L(bol) and z.
(3)
obtain the current best estimates of the far-IR emission, thus L(bol)
for
this
sample, and establish if the relative contribtuion of mid-to-far IR dust
emission
is correlated with morphology (resolved vs. unresolved).
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11143
Title:
NICMOS
imaging of submillimeter galaxies with CO and PAH redshifts
PI:
Andrew
Baker
PI
Institution:
Rutgers
the State University of New Jersey
We
propose to obtain F110W and F160W imaging of 10 z~2.4 submillimeter
galaxies
(SMGs) whose optical redshifts have been confirmed by the detection
of
millimeter CO and/or mid-infrared PAH emission. With
the 4000A break
falling
within/between the two imaging filters, we will be able to study these
sources'
spatially resolved stellar populations (modulo extinction) in the
rest-frame
optical. SMGs' large luminosities
appear to be due largely to
merger-triggered
starbursts; high-resolution NICMOS imaging will help us
understand
the stellar masses, mass ratios, and other properties of the merger
progenitors,
valuable information in the effort to model the mass assembly
history
of the universe.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11144
Title:
Building
on the Significant NICMOS Investment in GOODS: A Bright, Wide-Area
Search for
z>=7 Galaxies
PI:
Rychard
Bouwens
PI
Institution:
University
of California - Santa Cruz
One
of the most exciting frontiers in observational cosmology has been to
trace
the buildup and evolution of galaxies from very early times. While
hierarchical
theory teaches us that star formation in galaxies likely starts
out
small and builds up gradually, only recently has it been possible to see
evidence
for this observationally through the evolution of the LF from z~6 to
z~3. Establishing that this build up occurs
from even earlier times (z~7-8)
has
been difficult, however, due to the small size of current high-redshift
z~7-8
samples -- now numbering in the range of
~4-10 sources. Expanding
the
size
of these samples is paramount, if we are to push current studies of
galaxy
buildup back to even earlier times.
Fortunately, we should soon be
able
to do so, thanks to ~50 arcmin**2 of deep (26.9 AB mag at 5 sigma)
NICMOS
1.6
micron data that will be available over the two ACS GOODS fields as a
result
of one recent 180-orbit ACS backup program and a smaller program.
These
data will nearly triple the deep near-IR imaging currently available
over
these fields and therefore represent a significant resource for finding
and
characterizing the brightest and likely most massive high-redshift
sources
(which
can be found in no other way but with wide-area searches).
To make
maximal
use of these data, we will first isolate a small sample of the most
interesting,
candidate z>=7 galaxies from this survey through their z-H
colours. We then propose to follow-up each
of these candidates with NICMOS
imaging
at 1.1 microns ('J'-band) to determine which of these sources are at
z>=7
and thus significantly expand our sample of luminous, z>=7 galaxies.
Since
preliminary studies indicate that these candidates occur in only 30% of
the
NIC3 fields, our follow-up strategy is ~3 times as efficient as without
this
preselection and 9 times as efficient as a search in a field with no
pre-
existing
data. We expect to identify ~8
luminous z-dropouts and possibly ~2
z~10
J-dropouts as a result of this program, more than tripling the number
currently
known. The increased sample sizes
are important if we are to
solidify
current conclusions about galaxy buildup and the evolution of the LF
from
z~8. In addition to the high
redshift science, these deep 1.1 micron
data
would have significant value for many diverse endeavors, including (1)
improving
our constraints on the stellar mass density at z~7-10 and (2)
doubling
the number of galaxies at z~6 for which we can estimate dust
obscuration.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11145
Title:
Probing
the Planet Forming Region of T Tauri Stars in Chamaeleon
PI:
Nuria
Calvet
PI
Institution:
University
of Michigan
By
studying the inner, planet-forming regions of circumstellar disks around
low-mass
pre-main sequence stars we can refine theories of giant planet
formation
and develop timescales for the evolution of disks and their planets.
Spitzer
infrared observations of T Tauri stars in the Chamaeleon star-forming
region
have given us an unprecedented look at dust evolution in young objects.
However,
despite this ground breaking progress in studying the dust in young
disks,
the gas properties of the inner disk remain essentially unknown. Using
ACS
on HST, we propose to measure the H_2
emission originating in the
innermost
disk regions of classical T Tauri stars in different stages of
evolution
with the objective of revealing the timescales of gas dissipation
and
its relationship to dust evolution.
This proposal is part of a
comprehensive
effort with approved programs on Spitzer, Gemini, and Magellan
that
aim to characterize the state of gas and dust in disks where planets may
already
have formed.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM IN EXTERNAL GALAXIES
ID:
11146
Title:
The
Role of Stellar Feedback in Galaxy Evolution
PI:
Daniela
Calzetti
PI
Institution:
University
of Massachusetts
Stellar
feedback - the return of mass and energy from star formation to the
interstellar
medium - is one of the primary engines of galaxy evolution. Yet,
the
observational canvass of feedback is incomplete. We propose to
investigate
this
fundamental aspect of star formation on one local actively star-forming
galaxy,
He2-10, selected to occupy an
unexplored niche in the key parameter
space
of stellar mass. The WFPC2
narrow-band observations in the light of H-
beta,
[OIII], H-alpha, and [SII] will: (1)
discriminate the feedback-induced
shock
fronts from the photoionized regions; (2) map, and provide a complete
census
of, the shocks inside and around the starburst regions; and (3) measure
the
energy budget of the star-formation-produced shocks. These observations,
joined
by our previous data and studies on starbursts, will yield: (1) the
efficiency
of the feedback, i.e. the fraction of the star formation's
mechanical
energy transported out of the starburst volume rather than radiated
away,
in the dual-parameter space of host's stellar mass and star formation
intensity;
(2) the conditions under which feedback morphs from a localized
process
to a galactic scale mechanism. The high angular resolution of HST is
crucial
for separating the spatially narrow shock fronts (~10 pc=0.2" at 10
Mpc)
from the more extended photoionization fronts. This project will provide
the
most comprehensive quantitative foundation of stellar feedback and a
gauge
for
determining the role of feedback in the energetics, structure and star
formation
history of galaxies.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11147
Title:
The
Origin of Diffuse UV Light from Spiral Disks
PI:
Rupali
Chandar
PI
Institution:
Carnegie
Institution of Washington
The
ultraviolet light from galaxies has been used as a beacon for tracing
the
cosmic
star formation history of the Universe, yet we have an incomplete
understandingof
many characteristics of this light.
Most of the UV emission
from
nearby, normal star--forming galaxies is unresolved and "diffuse",
and
GALEX
has shown that in spiral disks it permeates the inter-arm regions. The
nature
of this diffuse inter-arm component is under debate.
Recent results
suggest
that it may arise from non-ionizing UV photons which originate in star
forming
regions in the spiral arms, travel in the plane of the galaxy, and
then
scatter off of diffusely distributed cold dust grains.
Alternatively, an
in-situ,
unresolved stellar population could produce the observed inter-arm UV
emission. This project seeks to establish which
of the two competing
scenarios
is responsible for the bulk of this diffuse emission.
We propose to
use
HST's UV imaging capability (ACS/SBC) to obtain deep observations of
selected
fields in the nearby spiral galaxy M101, for which available (low
angular
resolution) data favor the 'scattered light' scenario.
Our
observations
are designed to detect any faint, UV-luminous stellar population
down
to main sequence B5 stars. With
these data, we will establish the nature
of
the bulk of the diffuse UV light in this spiral galaxy by:
(i)
quantifying
the
contribution from dust-scattered light; (ii) measuring the contribution
to
the
ubiquitous diffuse ionized medium from in-situ ionizing stars; and (iii)
providing
constraints on the observed stellar mass function in the field.
Only
HST has the UV sensitivity and angular resolution to discriminate
in-situ
stellar
populations from scattered light.
The ultimate goal of this project
is
to re-'calibrate' the UV emission as a star formation rate indicator,
which
will
need to account for any scattered component.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11148
Title:
High
Contrast Imaging of Dusty White Dwarfs
PI:
John
Debes
PI
Institution:
Carnegie
Institution of Washington
For
the past 18 years, only one white dwarf with a circumstellar dust disk
was
known
to exist. In the last two years,
six new disks have been discovered.
Since
all material inwards of a few AU should be scoured clean during post
main
sequence evolution, the primary explanation is the presence of a
planetary
system that is perturbing relic planetesimals into the tidal
disruption
radius of the white dwarf. Dusty
disks around white dwarfs should
be
markers for planets and we propose to use high contrast imaging to
search
for
faint companions down to 6 M_$J$ that may be feeding the disks. White
dwarfs
are uniquely suited for planet searches, where the planet/white dwarf
contrast
is less than for main sequence stars.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11149
Title:
Characterizing
the Stellar Populations in Lyman-Alpha Emitters and Lyman Break
Galaxies at
5.7<z<7 in the Subaru Deep Field
PI:
Eiichi
Egami
PI
Institution:
University
of Arizona
The
epoch of reionization marks a major phase transition of the Universe,
during
which the intergalactic space became transparent to UV photons.
Determining
when this occurred and the physical processes involved represents
the
latest frontier in observational cosmology. Over the last few years,
searches
have intensified to identify the population of high-redshift (z>6)
galaxies
that might be responsible for this process, but the progress is
hampered
partly by the difficulty of obtaining physical information (stellar
mass,
age, star formation rate/history) for individual sources. This is
because
the number of z>6 galaxies that have both secure spectroscopic
redshifts
and high-quality infrared photometry (especially with Spitzer/IRAC)
is
still fairly small. Considering that only several photometric points are
available
per source, and that many model SEDs are highly degenerate, it is
crucial
to obtain as many observational constraints as possible for each
source
to ensure the validity of SED modeling. To better understand the
physical
properties of high-redshift galaxies, we propose here to conduct
HST/NICMOS
(72 orbits) and Spitzer/IRAC (102 hours) imaging of
spectroscopically
confirmed, bright (z<26 mag (AB)) Ly-alpha emitters (LAEs)
and
Lyman-break galaxies (LBGs) at 5.7<z<7 selected from the Subaru
Deep
Field.
Spectroscopic redshifts remove one critical free parameter from SED
modeling
while bright source magnitudes ensure high-quality photometric data.
By
making accurate determinations of stellar masses, ages, and
star-formation
histories,
we will specifically address the following major questions: (1)
Do
LAEs
and LBGs represent physically different galaxy populations at z>6 as
suggested
recently? (2) Is Ly-alpha emission systematically suppressed at z>6
with
respect to continuum emission? (i.e., are we reaching the epoch of
incomplete
reionization?), and (3) Do we see any sign of abnormally young
stellar
population in any of the z>6 galaxies?
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11150
Title:
Beta
Pic Polarimetry with NICMOS
PI:
James
Graham
PI
Institution:
University
of California - Berkeley
Debris
disk stars host transient dust grains that comprise a collisional
cascade
with sizes ranging from planetesimals to the sub-micron. In addition
to
the gravity of the host star and any planets present, these grains are
subject
to size-dependent non-gravitational forces, e.g., corpuscular drag and
radiation
pressure. When a steep spectrum of grain sizes prevails, such as the
Dohnanyi
distribution, scattered light images preferentially trace grains with
dimensionless
size parameter of order unity. Thus images in scattered
starlight
provide unique windows on the balance of forces acting on grains at
a
specific size. Therefore, in an A star system such as beta Pic, the
near-IR
is
dominated by grains close to the blow out size and therefore NICMOS
traces
dust
on hyperbolic orbits. Scattering
is fundamentally polarization
sensitive,
and measurements that record intensity literally see only half the
picture.
If linear polarization is measured then the elements of the complex
scattering
matrix can be reconstructed. These matrix elements provide
fundamental
constraints on the size, composition and structure of the
scatterers.
Notably, polarimetry can be used to break the degeneracy between
scattering
asymmetry, g, and the radial dust gradient, which are otherwise
covariant
in an edge-on disk. Thus, we can use polarimetry to localize the
parent
bodies in the beta Pic disk. In
beta Pic, dust is thought to originate
mainly
from the sublimation of cometary bodies near periastron. The
irradiation
of cometary material leads to sublimation and photodissociation of
ices
forming porous grains consisting of a matrix of refractory material.
Such
grains
have a characteristic scattering signature in polarized light that can
be
distinguished from compact grains that arise from collisional erosion of
asteroidal
material.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11151
Title:
Evaluating
the Role of Photoevaporation of Protoplanetary Disk Dispersal
PI:
Gregory
Herczeg
PI
Institution:
California
Institute of Technology
Emission
produced by accretion onto the central star leads to
photoevaporation,
which may play a fundamental role in disk dispersal.
Models
of
disk photoevaporation by the central star are challenged by two
potential
problems: the emission
produced by accretion will be substantially weaker for
low-mass
stars, and photoevaporation must continue as accretion slows.
Existing
FUV spectra of CTTSs are biased to solar-mass stars with high
accretion
rates, and are therefore insufficient to address these problems. We
propose
use HST/ACS SBC PR130L to obtain FUV spectra of WTTSs and of CTTSs at
low
masses and mass accretion rates to provide crucial data to evaluate
photoevaporation
models. We will estimate the FUV
and EUV luminosities of
low-mass
CTTSs with small mass accretion rates, CTTSs with transition disks
and
slowed accretion, and of magnetically-active WTTSs.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11152
Title:
Probing
the compact dust disk of a nearby Classical T Tauri Star
PI:
Bruce
Macintosh
PI
Institution:
Lawrence
Livermore National Laboratory
BP
Psc is a high Galactic latitude (b = -57), bright, IRAS source that
generally
has been classified as a T Tauri star but little studied to date. We
have
carried out a multiwavelength ground-based study of this object and find
that
it is most likely a ~10 Myr classical T Tauri star surrounded by a gas
and
dust disk, and less than 100 pc from Earth, making it one of the oldest
and
closest such stars known. Near-IR AO images and IR photometry show it is
surrounded
by an compact (0.2"), almost-edge-on, optically
thick disk of dust
with
a wide range of temperatures. We propose a multiwavelength polarimetric
study
of the compact disk to support quantitative modeling to recover disk and
dust
parameters. We also propose coronagraphic imaging to search for larger-
scale
dust structures invisible in ground-based images, and narrowband imaging
of
an outflow jet and associated Herbig-Haro objects to study their
structure
and
determine a kinematic distance of the system. A massive compact disk
surrounding
an isolated 10 Myr star is a unique environment for planet
formation,
and its proximity to Earth allows HST to study it in detail.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11153
Title:
The
Physical Nature and Age of Lyman Alpha Galaxies
PI:
Sangeeta
Malhotra
PI
Institution:
Arizona
State University
In
the simplest scenario, strong Lyman alpha emission from high redshift
galaxies
would indicate that stellar populations younger than 10 Myrs dominate
the
UV. This does not, however, constrain the stellar populations older than
100
Myrs, which do not contribute to UV light. Also,
the Lyman alpha line can
be
boosted if the interstellar medium is both clumpy and dusty. Different
studies
with small samples have reached different conclusions about the
presence
of dust and old stellar populations in Lyman alpha emitters. We
propose
HST-NICMOS and Spitzer-IRAC photometry of
35 Lyman-alpha galaxies at
redshift
4.5<z<6.5, in order to determine their spectral energy
distribution
(SED)
extending through rest-frame optical. This will allow us to measure
accurately
(1) The total stellar mass in these objects, including old stars
which
may have formed at redshifts (z > 8) not easily probed by any other
means. (2) The dust extinction in the
rest-frame UV, and therefore a
correction
to their present star-formation rates.
Taken together, these two
quantities
will yield the star-formation histories of Lyman alpha galaxies,
which
form fully half of the known galaxies at z=4-6. They will tell us
whether
these are young or old galaxies by straddling the 4000A break. Data
from
NICMOS is essential for these compact and faint (i=25-26th magnitude AB)
high
redshift galaxies, which are too faint for good near-IR photometry from
the
ground.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11154
Title:
Optical-UV
Spectrum of the Middle-aged Pulsar B1055-52
PI:
George
Pavlov
PI
Institution:
The
Pennsylvania State University
The
middle-aged radio, X-ray and gamma-ray pulsar B1055-52 is one of the few
pulsars
that allow a multiwavelength study of pulsar radiation. An optical
counterpart
of the pulsar has been detected with the HST FOC, but it was
observed
in only one filter (F342W, m=24.9). To understand the nature of the
pulsar
radiation, its spectrum must be measured in a broad wavelegth range. We
propose
imaging observations of the pulsar's counterpart with
WFPC2 in the
red
part of the spectrum and ACS/SBC in the UV part to measure the broadband
spectral
distribution, compare it with the X-ray spectrum, and investigate the
thermal
and magnetospheric components of the pulsar's radiation.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11155
Title:
Dust
Grain Evolution in Herbig Ae Stars:
NICMOS
Coronagraphic Imaging and Polarimetry
PI:
Marshall
Perrin
PI
Institution:
University
of California - Berkeley
We
propose to take advantage of the sensitive coronagraphic capabilities of
NICMOS
to obtain multiwavelength coronagraphic imaging and polarimetry of
primordial
dust disks around young intermediate-mass stars (Herbig Ae stars),
in
order to advance our understanding of how dust grains are assembled into
larger
bodies. Because the polarization
of scattered light is strongly
dependent
on scattering particle size and composition, coronagraphic imaging
polarimetry
with NICMOS provides a uniquely powerful tool for measuring grain
properties
in spatially resolved circumstellar disks. It
is widely believed
that
planets form via the gradual accretion of planetesimals in gas-rich,
dusty
circumstellar disks, but the connection between this suspected process
and
the circumstellar disks that we can now observe around other stars
remains
very
uncertain. Our proposed
observations, together with powerful 3-D
radiative
transfer codes, will enable us to quantitatively determine dust
grain
properties as a function of location within disks, and thus to test
whether
dust grains around young stars are in fact growing in size during the
putative
planet-formation epoch. HST
imaging polarimetry of Herbig Ae stars
will
complement and extend existing polarimetric studies of disks around
lower-mass
T Tauri stars and debris disks around older main-sequence stars.
When
combined with these previous studies, the proposed research will help us
establish
the influence of stellar mass on the growth of dust grains into
larger
planetesimals, and ultimately to planets.
Our results will also let us
calibrate
models of the thermal emission from these disks, a critical need for
validating
the properties of more distant disks inferred on the basis of
spectral
information alone.
======================================================================
Proposal
Category: SNAP
Scientific
Category: SOLAR SYSTEM
ID:
11156
Title:
Monitoring
Active Atmospheres on Uranus and Neptune
PI:
Kathy
Rages
PI
Institution:
SETI
Institute
We
propose Snapshot observations of Uranus and Neptune to monitor changes
in
their
atmospheres on time scales of weeks and months. Uranus
equinox is only
months
away, in December 2007. Hubble
Space Telescope observations during the
past
several years (Hammel et al. 2005, Icarus 175, 284 and references
therein)
have revealed strongly wavelength-dependent latitudinal structure,
the
presence of numerous visible-wavelength cloud features in the northern
hemisphere,
at least one very long-lived discrete cloud in the southern
hemisphere,
and in 2006 the first dark spot ever seen on Uranus.
Long-term
ground-based
observations (Lockwood and Jerzekiewicz, 2006, Icarus 180, 442;
Hammel
and Lockwood 2007, Icarus 186, 291) reveal seasonal brightness changes
whose
origins are not well understood. Recent near-IR images of Neptune
obtained
using adaptive optics on the Keck Telescope, together with HST
observations
(Sromovsky et al. 2003, Icarus 163, 256 and references therein)
which
include previous Snapshot programs (GO 8634, 10170, 10534) show a
general
increase in activity at south temperate latitudes until 2004, when
Neptune
returned to a rather Voyager-like appearance. Further
Snapshot
observations
of these two dynamic planets will elucidate the nature of long-
term
changes in their zonal atmospheric bands and clarify the processes of
formation,
evolution, and dissipation of discrete albedo features.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11157
Title:
NICMOS
Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar
Mass
Spectrum
PI:
Joseph
Rhee
PI
Institution:
University
of California - Los Angeles
Association
of planetary systems with dusty debris disks is now quite secure,
and
advances in our understanding of planet formation and evolution can be
achieved
by the identification and characterization of an ensemble of debris
disks
orbiting a range of central stars with different masses and ages.
Imaging
debris disks in starlight scattered by dust grains remains technically
challenging
so that only about a dozen systems have thus far been imaged. A
further
advance in this field needs an increased number of imaged debris
disks. However, the technical challege of such
observations, even with the
superb
combination of HST and NICMOS, requires the best targets.
Recent HST
imaging
investigations of debris disks were sample-limited not limited by the
technology
used. We performed a search for
debris disks from a IRAS/Hipparcos
cross
correlation which involved an exhaustive background contamination check
to
weed out false excess stars. Out
of ~140 identified debris disks, we
selected
22 best targets in terms of dust optical depth and disk angular size.
Our
target sample represents the best currently available target set in
terms
of
both disk brightness and resolvability.
For example, our targets have
higher
dust optical depth, in general, than newly identified Spitzer disks.
Also,
our targets cover a wider range of central star ages and masses than
previous
debris disk surveys. This will help us to investigate planetary
system
formation and evolution across the stellar mass spectrum.
The
technical
feasibility of this program in two-gyro mode guiding has been proven
with
on-orbit calibration and science observations during HST cycles 13, 14,
and
15.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11158
Title:
HST
Imaging of UV emission in Quiescent Early-type Galaxies
PI:
R.
Rich
PI
Institution:
University
of California - Los Angeles
We
have constructed a sample of early type galaxies at z~0.1 that have blue
UV-optical
colors, yet also show no signs of optical emission, or extended
blue
light. We have cross-correlated
the SDSS catalog and the Galaxy
Evolution
Explorer Medium Imaging Survey to select a sample of galaxies where
this
UV emission is strongest. The origin of the UV rising flux in these
galaxies
continues to be debated, and the possibility that some fraction of
these
galaxies may be experiencing low levels of star formation cannot be
excluded. There is also a possibility that
low level AGN activity (as
evidenced
by a point source) is responsbile
We propose to image the UV
emission
using the HST/SBC and to explore the morphology of the UV emission
relative
to the optical light.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11159
Title:
The
True Galactic Bulge Luminosity Function
PI:
R.
Rich
PI
Institution:
University
of California - Los Angeles
We
propose to obtain second epoch imaging of the deep Galactic bulge field
observed
using NICMOS by Zoccali et al. (2000).
The bulge luminosity and mass
function
suffered from 30-50% contamination by foreground disk stars, which
was
impossible to correct for in the original study. Revisiting
the field
after
9 years, we propose to segregate the foregound disk stars because they
have
large transverse velocities, thus revealing the luminosity function of
Galactic
bulge low mass stars to near the hydrogen burning limit.
The slope
of
the mass function has implications for galaxy formation and for
understanding
the nature of microlensing in the Galactic bulge.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11160
Title:
Escape
fraction and stellar populations in a highly magnified Lyman-Break
Galaxy
PI:
Johan
Richard
PI
Institution:
California
Institute of Technology
Understanding
how star-forming galaxies contribute to cosmic reionization is
one
of the frontiers of observational cosmology. A key ingredient in this
issue
is measuring the escape fraction of Lyman-continuum photons in high
redshift
galaxies (z>3). Gravitationally lensed Lyman-break galaxies (LBGs)
act
as important laboratories for studying the resolved physical properties
at
sub-kpc
scales with high signal-to-noise. Correlating the local escape
fraction
with physical parameters derived from stellar population modeling
(such
as the star formation rate, age and reddening) will offer new insights
into
understanding the physical processes involved with the production of
ionizing
photons. We propose here follow-up
observations of the "Cosmic Eye",
a
remarkable, highly magnified (x 30), Lyman-break galaxy at z~3.07 using
WFPC2
and NICMOS. Deep ultraviolet WFPC2 imaging will provide a detailed study
of
variations in the escape fraction, while WFPC2 and NICMOS/NIC2 imaging
will
complement
the current broad-band detections to allow a precise modeling of
the
spatially-dependent spectral energy distribution. This will allow the
first
comprehensive analysis between the escape fraction, the local SED and
the
dynamics of a distant galaxy.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11161
Title:
Revealing
the Explosion Geometry of Nearby GRB-SNe
PI:
Alicia
Soderberg
PI
Institution:
California
Institute of Technology
The
connection between gamma-ray bursts and Type Ibc supernovae is well-
established
in broad terms. However, our
recent identification of an
intermediate
class of sub-energetic GRBs, and the overall overlap in Nickel
production
between GRB-SNe and ordinary SNe Ibc suggest that the properties
leading
to the production of a relativistic engine are yet to be uncovered. A
fundamental
difference between the two classes of explosions may be imprinted
in
the overall geometry of the explosion. The relativistic component of
GRBs
is
known to be highly collimated, but it is unclear if the SN blast is
spherical
or mildly collimated as well. Here we propose HST observations of
the
late (>30 days) decay tails of two GRB-SNe as an independent measure
of
the
Nickel mass synthesized in the explosion.
A comparison to the Nickel mass
inferred
from the peak brightness of the SNe will provide a direct measure of
the
explosion asymmetry, since at late time the explosion is essentially
spherical.
These observations will form the core of a multi-wavelength
(optical,
X-ray, radio) effort to fully characterize all aspects of the
explosions,
from the energy and geometry of the relativistic material (VLA,
Chandra)
to the early SN evolution (Keck, Magellan). The
proposed
observations
require two slow-response (>30 days) TOOs, ideally suited to the
2-gyro
operations of HST.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11162
Title:
Understanding
the Long Term Impacts of Low Magnetic Accretion
PI:
Paula
Szkody
PI
Institution:
University
of Washington
The
low accretion rate Polar EF Eri has been in a low state for more than 9
years.
Our recent GALEX photometry revealed a source of UV light that is
producing
more flux than the white dwarf and which is highly modulated on the
81
min orbital period of the system. We request UV spectra with the SBC on
the
ACS
to resolve whether limb darkening or cyclotron emission can explain the
observed
phenomena and provide insight on the long term heating effects under
low
accretion scenarios.
======================================================================
Proposal
Category: GO
Scientific
Category: HOT STARS
ID:
11163
Title:
Accreting
Pulsating White Dwarfs in Cataclysmic Variables
PI:
Paula
Szkody
PI
Institution:
University
of Washington
Recent
ground-based observations have increased the number of known pulsating
white
dwarfs in close binaries with active mass transfer (cataclysmic
variables)
from 5 to 11 systems. Our past Cycles 8 and 11 STIS observations of
the
first 2 known, followed by our Cycle 13 SBC observations of the next 3
discovered,
revealed the clear presence of the white dwarf and increased
amplitude
of the pulsations in the UV compared to the optical. The
temperatures
derived from the UV spectra show 4 systems are much hotter than
non-interacting
pulsating white dwarfs. A larger sample is needed to sort out
the
nature of the instability strip in accreting pulsators i.e. whether
effects
of composition and rotation due to accretion result in a well-defined
instability
strip as a function of Teff.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11164
Title:
Molecular
Hydrogen Disks Around T Tauri Stars
PI:
David
Weintraub
PI
Institution:
Vanderbilt
University
We
propose to measure the properties of planetary system-sized disks around
Sun-like,
pre-main sequence stars by imaging the inner parts of these disks
for
the first time in gaseous emission from their most dominant constituent,
molecular
hydrogen gas. Specifically, we will use the F212N filter and NICMOS
to
determine the spatial distribution of ro-vibrational H2 emission from
protoplanetary
disks around selected classical and weak-lined T Tauri stars.
The
target stars are among those detected by members of this team through
high
resolution,
ground-based infrared spectroscopy. The spectra reveal H2 emission
at
the rest velocities of the stars and at positions spatially coincident
with
the
stars at the spatial resolution of the spectroscopic data. This imaging
experiment,
which is impossible to do using ground-based facilities, is
possible
using the NICMOS camera aboard the HST because the point spread
function
of this system is extremely stable and can be measured to a very high
accuracy.
This experiment is an important test of the interpretation that the
2.122
micron H2 line emission seen toward T Tauri stars is produced at
distances
of 10 to 30 AU from the stars, the region in which giant planets are
expected
to form around these stars. These observations will contribute toward
developing
a better understanding of the process, likelihood, and timescale
for
the formation of planets around Sun-like stars.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11165
Title:
The
Radius of the "Super-Neptune" HD 149026b
PI:
Joshua
Winn
PI
Institution:
Massachusetts
Institute of Technology
Current
measurements suggest that the transiting exoplanet HD 149026b is a
"super-Neptune,"
with an enormous heavy-element core. The existence of such a
planet
is a major challenge to planet formation theories. We propose to place
the
radius measurement on much firmer footing, by obtaining a NICMOS light
curve
with 0.4 mmag precision and 13 sec cadence. We will improve the radius
measurement
by a factor of 2.3, and more importantly, the result will be more
robust
because we will determine the stellar radius directly from the data.
Numerous
attempts to do this from the ground have failed.
======================================================================
Proposal
Category: GO
Scientific
Category: AGN/QUASARS
ID:
11166
Title:
The
Mass-dependent Evolution of the Black Hole-Bulge Relations
PI:
Jong-Hak
Woo
PI
Institution:
University
of California - Santa Barbara
In
the local universe, the masses of giant black holes
are correlated with
the
luminosities, masses and velocity dispersions of their host galaxy
bulges.
This
indicates a surprisingly close connection between the evolution of
galactic
nuclei (on parsec scales) and of stars on kpc scales. A key
observational
test of proposed explanations for these correlations is to
measure
how they have evolved over cosmic time. Our ACS imaging of 20 Seyfert
1
galaxies at z=0.37 showed them to have smaller bulges (by a factor of
3) for
a
given central black hole mass than is found in galaxies in the
present-day
universe.
However, since all our sample galaxies had black hole masses in the
range
10^8.0--8.5 Msun, we could only measure the OFFSET in black hole mass to
bulge
luminosity ratios from the present epoch. By extending this study to
black
hole masses another factor of 10 lower, we propose to determine the full
CORRELATION
of black hole mass with host galaxy properties at a lookback time
of
4 Gyrs and to test mass-dependency of the evolution. We have selected 14
Seyfert
galaxies from SDSS DR5 whose narrow Hbeta emission lines (and
estimated
nuclear luminosities) imply that they have black hole masses around
10^7
Msuns. We will soon complete our Keck spectroscopic measures of their
bulge
velocity dispersions. We need a
1-orbit NICMOS image of each galaxy to
separate
its nonstellar luminosity from its bulge and disk. This will allow us
to
make the first determination of the full black hole/bulge relations at
z=0.37
(e.g. M-L and M-sigma), as well as a test of whether active galaxies
obey
the Fundamental Plane relation at that epoch.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11167
Title:
A
Unique High Resolution Window to Two Strongly Lensed Lyman Break
Galaxies
PI:
Sahar
Allam
PI
Institution:
Fermi
National Accelerator Laboratory (FNAL)
On
rare occasions, the otherwise very
faint Lyman Break Galaxies (LBGs) are
magnified by gravitational lensing to provide
exceptional targets for
detailed
spectroscopic and imaging studies. We propose HST WFPC2 and NICMOS
imaging
of two strongly lensed Lyman Break Galaxies (LBGs)
that were recently
discovered by members of our
team. These
two LBGs -- the "8 O'Clock Arc"
and
the "SDSS J1206+5142
Arc" -- are currently the
brightest known LBGs,
roughly
3 times brighter than the
former record-holder, MS1512-cB58
(a.k.a.
"cB58").
The z=2.73 "8 O'Clock Arc" extends ~10 arcsec in length and is
magnified
by a factor of 12. The z=2.00
"SDSS J1206+5142 Arc" also extends
~10
arcsec in length and is magnified by a factor of 30.
Due to their
brightness
and magnification, these two strongly lensed LBGs offer an
unprecedented
opportunity for the very detailed investigation of two
individual
galaxies at high redshift.
We are currently pursuing a vigorous
ground-based
campaign to obtain multi-wavelength (UV,
optical, NIR, radio)
observations
of these two
LBGs, but our
campaign currently lacks a
means
of
obtaining high-resolution
optical/NIR imaging -- a lack that
currently
only
HST can address. Our prime objective for this proposal is to obtain high
resolution
HST images of these two systems with
two-orbit WFPC2 images in the
BVI
bands and two-orbit NICMOS/NIC2 images in the J
and H bands. These data
will
allow us to construct detailed lensing models, probe the mass and light
profiles
of the lenses and their environments, and constrain the star
formation
histories and rest-frame UV/optical spectral energy distributions of
the
LBGs.
======================================================================
Proposal
Category: GO
Scientific
Category: STAR FORMATION
ID:
11168
Title:
The
IMF in the Hidden Galactic Starburst W49A
PI:
Bernhard
Brandl
PI
Institution:
Universiteit
Leiden
W49A
is one of the most luminous and prolific massive star formation regions
in
the disk of our Milky Way. Given the presence of several very massive OB
clusters
as well as an unusually high concentration of many young ultra-
compact
HII regions (UCHIIR) -- all embedded in about 1 million solar masses
of
molecular gas -- it is arguably the best Galactic template for a
luminous
starburst
region. We propose to obtain
NICMOS imaging of the central part of
W49A,
covering a strip from the central, massive OB cluster to the ring of
UCHIIRs.
Our goals are to resolve and characterize the central star cluster
and
determine its IMF down to about 1 solar mass. We want to characterize
the
distribution
of intermediate-mass YSOs, and identify the NIR counterparts to
the
UCHIIRs. The combination of the proposed HST/NICMOS data with our
recently
obtained
Spitzer observations would allow a great step forward in the
understanding
of massive star and cluster formation.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11169
Title:
Collisions
in the Kuiper belt
PI:
Michael
Brown
PI
Institution:
California
Institute of Technology
For
most of the 15 year history of observations of Kuiper belt objects, it
has
been
speculated that impacts must have played a major role in shaping the
physical
and chemical characteristics of these objects, yet little direct
evidence
of the effects of such impacts has been seen. The past 18 months,
however,
have seen an explosion of major new discoveries giving some of the
first
insights into the influence of this critical process. From a diversity
of
observations we have been led to the hypotheses that:
(1) satellite-forming
impacts
must have been common in the Kuiper belt; (2) such impacts led to
significant
chemical modification; and (3) the outcomes of these impacts are
sufficiently
predictable that we can now find and study these impact-derived
systems
by the chemical and physical attributes of both the satellites and the
primaries.
If our picture is correct, we now have in hand for the first time a
set
of incredibly powerful tools to study the frequency and outcome of
collisions
in the outer solar system. Here we propose three linked projects
that
would answer questions critical to the multiple prongs of our
hypothesis.
In
these projects we will study the chemical effects of collisions through
spectrophotometric
observations of collisionally formed satellites and through
the
search for additional satellites around primaries with potential impact
signatures,
and we will study the physical effects of impacts through the
examination
of tidal evolution in proposed impact systems. The
intensive HST
program
that we propose here will allow us to fully test our new hypotheses
and
will provide the ability to obtain the first extensive insights into
outer
solar
system impact processes.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11170
Title:
UV
Imaging of the Martian Corona and the Escape of Hydrogen
PI:
John
Clarke
PI
Institution:
Boston
University
ACS
SBC UV imaging observations of Mars are proposed to study the extended
hydrogen
corona, with application to the escape of hydrogen and the history of
water
on Mars. These observations will
be scheduled when Mars is distant from
the
Earth, so that a field of view of +/- 4-5 Mars radii can be obtained to
image
the full range of the highly extended martian hydrogen corona through
its
H Ly alpha emission. The
observations will also be obtained when the Sun-
Earth-Mars
angle is close to 90 degrees, so that any asymmetry along the Mars-
Sun
line can be observed. The observed
2-dimensional brightness distribution
will
be related to local density using two existing radiative transfer codes,
and
the upward flux and velocity distributions will be determined by
comparison
with runs from an exospheric distribution model. These
observations,
combined with simultaneous Ly alpha observations by the SPICAM
instrument
on Mars Express from within the atmosphere, will provide the first
tight
constraints on the total escape flux and importance of nonthermal
processes
on the rate of escape.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM IN EXTERNAL GALAXIES
ID:
11171
Title:
Confirming
Light Echoes from SN 2006X in M100
PI:
Arlin
Crotts
PI
Institution:
Columbia
University in the City of New York
We
propose a minimal investment of spacecraft time to discover and confirm
a
light
echo from Supernova 2006X in M100, the closest Type Ia in many years.
Our
spectroscopic and photometric data indicate that this SN sits behind a
large
amount of interstellar dust likely to produce a strong echo signal.
This
is one of very few cases where we will be able to study the three-
dimensional
environment of a SN Ia in full detail, and begin to understand how
environmental
effects play into the evolutionary and observational factors
which
influence the utility of SN Ia as standard candles for probing
cosmology. We propose an efficient program to
definitively detect (or not) a
light
echo of reasonable signal strength, to confirm that it is an echo by
demonstrating
apparent superluminal motion if it exists, to map the three-
dimensional
geometry of the reflecting interstellar structures, and to detail
the
reflectance properties of the dust which can be used to constrain its
grain
size and composition distribution.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11172
Title:
Defining
Classes of Long Period Variable Stars in M31
PI:
Arlin
Crotts
PI
Institution:
Columbia
University in the City of New York
We
propose a thrifty but information-packed investigation (1440 exposures
total)
with NICMOS F205W, F160W and F110W providing crucial information about
Long
Period Variables in M31, at a level of detail that has recently allowed
the
discovery of new variable star classes in the Magellanic Clouds, a very
different
stellar population. These
observations are buttressed by an
extensive
map of the same fields with ACS and WFPC2 exposures in F555W and
F814W,
and a massive ground-based imaging patrol producing well-sampled light
curves
for more than 400,000 variable stars.
Our primary goal is to collect
sufficient
NIR data in order to analyze and classify the huge number of long-
period
variables in our catalog (see below) through Period-Luminosity (P/L)
diagrams. We will produce accurate P/L diagrams
for both the bulge and a
progression
of locations throughout the disk of M31.
These diagrams will be
similar
in quality to those currently in the Magellanic Clouds, with their
lower
metallicity, radically different star formation history, and larger
spread
in distance to the variables. M31
offers an excellent chance to study
more
typical disk populations, in a manner which might be extended to more
distant
galaxies where such variables are still visible, probing a much more
evenly
spread progenitor age distribution than cepheids (and perhaps useful as
a
distance scale alternative or cross-check). Our
data will also provide a
massive
and unique color-magnitude dataset, and
allow us to confirm the
microlensing
nature of a large sample of candidate lensed sources in M31. We
expect
that this study will produce several important results, among them a
better
understanding of P/L and P/L-color relations for pulsating variables
which
are essential to the extragalactic distance ladder, will view these
variables
at a common distance over a range of metallicities (eliminating the
distance-error
vs. metallicity ambiguity between the LMC and SMC), allow
further
insight into possible faint-variable mass-loss for higher
metallicities,
and in general produce a sample more typical of giant disk
galaxies
predominant in many studies.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11173
Title:
Completing
an Accurate Map of M31 Microlensing
PI:
Arlin
Crotts
PI
Institution:
Columbia
University in the City of New York
The
halo microlensing masses detected in the MACHO survey (claimed to
compose
about
20% of the Galaxy's mass) represent a major enigma in astrophysics, one
that
must be effectively cross-examined by an independent test.
We have
completed
a large, densely-sampled survey of M31 that can reveal in another
galaxy
such a halo microlensing signal if it exists. In
a previous
HST/ACS+WFPC2
program (GO 10273, Cycle 13, 16 orbits) we were able to learn
considerably
more about a subsample of these M31 microlensing events.
We were
pleased
to find that in most cases we could isolate the source star for each
event,
find its baseline flux and colors (essential for ruling out classes of
confusing
variable stars), test for misidentification of background
supernovae,
and measure the Einstein parameters, which constrain the range of
most
likely lens mass. (These Cycle 13
results are published in The
Astrophysical
Journal Letters.) We propose to
finish the job, taking a
similar
series of exposures to more than double the sample of well-constrained
microlensing
events, which together with the larger ground-based sample for
which
we are completing our analyses will provide 20-30 M31 bona fide
microlensing
events observed by HST. This will
be done via a series of
targetted
PC exposures, meant to maximize the number of candidates studied,
one
(or two) at a time. A sample of
this size and quality should be
sufficient
to settle the issue of a significant contribution to the halos of
galaxies
by stellar-mass lenses.
Furthermore, if there is a surplus of such
microlensing
events above what might be expected from stars alone, the higher
quality
of information will allow us to more accurately describe the spatial
distribution
of these lenses. We will also
complete several unique studies of
M31
stellar populations, both in support of the microlensing measurement and
in
their own right.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11174
Title:
A
Spitzer/X-ray candidate cluster at z>2:
NICMOS
imaging
PI:
Emanuele
Daddi
PI
Institution:
Commissariat
a l'Energie Atomique (CEA)
We
propose deep H-band imaging with NICMOS of a remarkable z>2 cluster
of
galaxy
candidate. Over a 1000 arcmin^2 field imaged with Spitzer's IRAC and
MIPS
we have discovered a compact (<30'' diameter) concentration of
extremely
red
galaxies with a factor of >40 overdensity over the adjacent field.
Among
these
galaxies for which we can derive meaningful photometric redshifts, 17
are
consistent with zphot=2-2.5, making very likely that the concentrationis
is
a real cluster at such high redshift. This is further supported by a 3.5
sigma
detection of extended X-Ray emission on Newton-XMM data, by a likely
color-magnitude
sequence of red galaxies, and by the presence of a giant
galaxy
consistent with a BCG at the cluster redshift. While spectroscopic
confirmation
of the cluster might result prohibitive with current facilities,
HST
high resolution imaging will allow us to gain crucial information for
the
study
and scientific exploitation of this hot gas hosting, record high-z
cluster
of galaxies. The HST high resolution observations will allow us to
unveil
the rest frame optical morphologies of
the galaxies and confirm the
presence
of ellipticals in the structure, detect and characterize the color-
magnitude
relation, measure their effective radii and construct their Kormendy
relation
for the passively evolving subsample, improve the photometric
redshift
estimates to confirm the real cluster nature of the structure,
estimate
stellar masses and check for possible deviations from the local mass-
size
relation, search for mergers and AGNs, and establish a cluster benchmark
for
cluster-field comparisons at this highest redshift.
======================================================================
Proposal
Category: GO
Scientific
Category: UNRESOLVED STELLAR POPULATIONS
ID:
11175
Title:
UV
Imaging to Determine the Location of Residual Star Formation in
Galaxies
Recently Arrived on the Red Sequence
PI:
Sandra
Faber
PI
Institution:
University
of California - Santa Cruz
We
have indentified a sample of low-redshift (z = 0.04 - 0.10) galaxies
that
are
candidates for recent arrival on the red sequence.
They have red optical
colors
indicative of old stellar populations, but blue UV-optical colors that
could
indicate the presence of a small quantity of continuing or very recent
star
formation. However, their spectra
lack the emission lines that
characterize
star-forming galaxies. We propose
to use ACS/SBC to obtain high-
resolution
imaging of the UV flux in these galaxies, in order to determine the
spatial
distribution of the last episode of star formation.
WFPC2 imaging
will
provide B, V, and I photometry to measure the main stellar light
distribution
of the galaxy for comparison with the UV imaging, as well as to
measure
color gradients and the distribution of interstellar dust.
This
detailed
morphological information will allow us to investigate the hypothesis
that
these galaxies have recently stopped forming stars and to compare the
observed
distribution of the last star formation with predictions for several
different
mechanisms that may quench star formation in galaxies.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11176
Title:
Location
and the Origin of Short Gamma-Ray Bursts
PI:
Andrew
Fruchter
PI
Institution:
Space
Telescope Science Institute
During
the past decade extraordinary progress has been made in determining the
origin
of long-duration gamma-ray bursts.
It has been conclusively shown
that
these objects derive from the deaths of massive stars.
Nonetheless, the
origin
of their observational cousins, short-duration gamma-ray bursts (SGRBs)
remains
a mystery. While SGRBs are
widely thought to result from the
inspiral
of compact binaries, this is a conjecture. A
number of hosts of
SGRBs
have been identified, and have been used by some to argue that SGRBs
derive
primarily from an ancient population (~ 5 Gyr); however, it is not
known
whether this conclusion more accurately reflects selection biases or
astrophysics. Here we propose to employ a variant of
a technique that we
pioneered
and used to great effect in elucidating the origins of long-duration
bursts. We will examine the degree to
which SGRB locations trace the red or
blue
light of their hosts, and thus old or young stellar populations. This
approach
will allow us to study the demographics of the SGRB population in a
manner
largely free of the distance dependent selection effects which have so
far
bedeviled this field, and should give direct insight into the age of the
SGRB
progenitor population.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11177
Title:
The
Nature of z=3 Lyman-Alpha Emitters
PI:
Caryl
Gronwall
PI
Institution:
The
Pennsylvania State University
The
advent of large mosaic CCD cameras on 4 -- 8 m class telescopes has
recently
led to a revolution in our ability to detect primordial galaxies.
Today,
large numbers of strong Ly-alpha
emitters (LAEs) are being discovered
between
2.4 < z < 6. These are
important objects: not
only do they sample a
part
of the galaxy luminosity function that is inaccessible to the
Lyman-break
technique,
but they also tend to be younger and less chemically evolved. In
fact,
the LAEs now being found are currently our best candidates for galaxies
in
the act of formation. To
investigate the properties of this class of
objects,
we have conducted an extremely deep narrow-band (5000 Angstrom; FWHM
=
50 Angstrom) and broad-band (UBVRIzJK) survey of the Extended Chandra
Deep
Field
South, and have identified a homogeneous sample of strong Ly-alpha
emitters
at z = 3.11. Twenty-seven of these
objects are located within the
region
surveyed by Great Observatories Origins Deep Survey (GOODS) and have
detailed
morphological information available from the rest-frame ultraviolet.
We
propose 0.2" resolution narrow-band imaging of 11 of our LAEs using the
F502N
filter of WFPC2. By comparing the
Ly-alpha and rest-frame UV continuum
morphologies
of these galaxies, we will be able to look for the presence of
outflows,
constrain their dust content, and test whether these objects are
truly
primordial galaxies.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11178
Title:
Probing
Solar System History with Orbits, Masses, and Colors of Transneptunian
Binaries
PI:
William
Grundy
PI
Institution:
Lowell
Observatory
The
recent discovery of numerous transneptunian binaries (TNBs) opens a
window
into
dynamical conditions in the protoplanetary disk where they formed as
well
as
the history of subsequent events which sculpted the outer Solar System
and
emplaced
them onto their present day heliocentric orbits. To
date, at least
43
TNBs have been discovered, but only about a dozen have had their mutual
orbits
and separate colors determined, frustrating their use to investigate
numerous
important scientific questions.
The current shortage of data
especially
cripples scientific investigations requiring statistical
comparisons
among the ensemble characteristics.
We propose to obtain
sufficient
astrometry and photometry of 23 TNBs to compute their mutual orbits
and
system masses and to determine separate primary and secondary colors,
roughly
tripling the sample for which this information is known, as well as
extending
it to include systems of two near-equal size bodies.
To make the
most
efficient possible use of HST, we will use a Monte Carlo technique to
optimally
schedule our observations.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11179
Title:
Dynamics
of Clumpy Supersonic Flows in Stellar Jets and in the Laboratory
PI:
Patrick
Hartigan
PI
Institution:
Rice
University
We
propose to reobserve three stellar jets in order to quantify how rapidly
clumps
in these flows accelerate and decelerate, and to compare the results
with
ongoing numerical simulations and laboratory experiments. Each jet has
been
imaged twice before with HST, and precise proper motions have been
measured
for all emitting knots in the jets. Images from the first two epochs
show
clear differential motions between adjacent clumps, as well as shear,
and
possibly
fragmentation. The proposed third epoch will enable us to measure the
first
ever accelerations in jets, quantify errors in existing proper motion
measurements,
and observe in real time how fluid instabilities develop in
supersonic
flows. The new images will make it possible to compare the behavior
of
astrophysical flows directly with numerical simulations and with
laboratory
experiments
of bow shocks and clumpy flows in progress at the Omega laser
facility.
======================================================================
Proposal
Category: GO
Scientific
Category: COOL STARS
ID:
11180
Title:
The
Morphology of the Post-Red Supergiant IRC+10420's Circumstellar Ejecta
PI:
Roberta
Humphreys
PI
Institution:
University
of Minnesota - Twin Cities
The
extremely luminous post-red supergiant and powerful OH/IR source IRC
+10420
is surrounded by a complex circumstellar nebula. Numerous small
condensations,
arcs, jet-like rays of knots, and intriguing semi-circular
structures
are easily visible in our previous WFPC2 images. We have suggested
that
these spatially recognizable features may be evidence for episodic mass
loss
events possibly from localized active regions. We now propose to obtain
second
epoch WFPC2 images with the Planetary Camera to measure the transverse
motions
of these ejecta. Spatially resolved spectra from STIS showed that the
embedded
arcs are kinematically distinct from the spherically expanding
diffuse
nebulosity. The transverse motions in combination with radial
velocities
from the STIS spectra, will let us determine the morphology of IRC
+10420's
nebula and the structures embedded in it, its mass loss history, and
provide
clues to the mass loss mechanism responsible for the discrete
ejections.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11181
Title:
SAINTS
- Supernova 1987A INTensive Survey
PI:
Robert
Kirshner
PI
Institution:
Harvard
University
SAINTS
is a program to observe SN 1987A, the brightest supernova in 383 years,
as
it matures into the youngest supernova remnant at age 20.
HST is the
essential
tool for spatially-resolved observations of SN1987A's many
components. A violent encounter is now underway
between the fastest-moving
debris
and the circumstellar ring: the shock
excites "hotspots." The
optical,
infrared
and X-ray fluxes are rising rapidly on 6-month time scales:
we
have
organized
HST, SPITZER, and CHANDRA observations to understand these regions.
In
Cycle 16, the separate hotspots may begin to fuse as the shock fully
enters
the
circumstellar ring. Photons from
these shocks will excite previously
invisible
gas outside the ring, revealing the true extent of the mass loss
that
preceded the explosion of Sanduleak -69 202. The inner debris of the
explosion,
excited by radioactive isotopes from the explosion, is now resolved
and
seen to be aspherical, providing direct evidence on the asymmetry of the
explosion. Questions about SN 1987A remain
unanswered. How did the enigmatic
three
rings form? Precisely what
happened during the core collapse and
bounce? Is a black hole or a neutron star left
behind? The rich and deep
data
set from SAINTS will help answer these central questions of supernova
science.
======================================================================
Proposal
Category: GO
Scientific
Category: RESOLVED STELLAR POPULATIONS
ID:
11182
Title:
The
Mass of the Milky Way:
Orbits
for Leo I and Leo II: Second Epoch Imaging of Leo II
PI:
Konrad
Kuijken
PI
Institution:
Universiteit
Leiden
Constraining
the mass of the Galaxy at large radii remains a difficult
problem. Available data are still rather scarce,
and orbits of even a few
objects
at large radii can have a large impact.
We propose to obtain proper
motions
for the two satellites Leo I and Leo II, which orbit the Galaxy at
about
200 kpc. Together with the radial
velcoities of these glaaxies, which
are
well known, the proper motions allow space velocities ot be consructed:
these
can remove signifiicant uncertainty in the Galactic mass models, and in
particular
settle the vexed question of whether or not Leo I is
gravitationally
bound to the Galaxy. The proper
motion of Leo I is addressed
in
a companion archival proposal; here we address the WFPC2 imagery of Leo
II.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM IN EXTERNAL GALAXIES
ID:
11183
Title:
Ultraviolet
Imaging of Lyman-Alpha-Selected Galaxies at High Redshift
PI:
Crystal
Martin
PI
Institution:
University
of California - Santa Barbara
We
propose to carry out deep NICMOS/NIC2 imaging in the rest-frame,
ultraviolet
continuum of galaxies discovered in the Magellan Multi-Slit Lyman
Alpha
Survey. This spectroscopic survey
identified
ultra-faint, redshift 5.7
Lyman-alpha
emitters (LAEs) in a 15 nm wide, OH-free band at 819 nm.
Imaging
with
HST is the only way to measure their continuum intensity near rest-frame
160
nm. The ultraviolet photometry
will directly measure the rate of star
formation
in common objects; and, when combined with groundbased Lyman-alpha
luminosities,
provide a reliable cross-calibration of Lyman-alpha attenuation
and
emission equivalent width. Direct
measurement of the size of the star-
forming
regions, unresolved in the groundbased data, will extend measurements
of
the intensity of star formation to common objects in the high-redshift
universe. Gaseous outflows from these galaxies
are thought to be the source
of
their asymmetric line profiles, and area-averaged star formation rates
are
needed
to calibrate feedback recipes, as well as eventually extend the
Schmidt-Kennicutt
law to high-redshift. The three
targets proposed in
Cycle~16
lie in fields covered by major galaxy surveys, are not as bright as
the
unusually luminous sources identified by such surveys at high-redshift,
and
present an opportunity to study properties of more common galaxies at
high-redshift.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11184
Title:
Imaging
the Shock Precursor in Tycho's SNR
PI:
John
Raymond
PI
Institution:
Smithsonian
Institution Astrophysical Observatory
Cosmic
ray acceleration in supernova remant shocks requires shock precursors
where
particles are trapped by plasma turbulence. The
precursors also heat
and
compress the upstream gas, producing H alpha emission and affecting line
profiles. We propose to image the brightest
non-radiative shock in Tycho's
SNR
to measure the brightness and width of the precursor.
These measurements
will
constrain 2 key parameters in cosmic ray acceleration models, and they
will
improve the accuracy of shock speed and electron-ion equilibration
derived
from H alpha profiles.
======================================================================
Proposal
Category: GO
Scientific
Category: ISM AND CIRCUMSTELLAR MATTER
ID:
11185
Title:
Search
for H-poor/He-rich Inclusions and a Solution to the Abundance,
Temperature
Problems
PI:
Robert
Rubin
PI
Institution:
NASA
Ames Research Center
Our
recent abundance survey of a large sample of Galactic planetary nebulae
(PNe)
has led to the discovery of a group
of super-metal-rich nebulae whose
spectra
are characterized by prominent optical recombination lines (ORLs) from
C,
N, O, & Ne ions and a large Balmer discontinuity jump. The heavy
element
abundances
derived from ORLs for several PNe are more than an order of
magnitude
higher than those derived from the traditional method based on
collisionally
excited lines (CELs), while the Balmer jump yields electron
temperatures
(Te) significantly lower than values derived from the [O III]
5007/4363
CEL line ratio. A
proposition that aspires to explain both the
nebular
abundance and Te problems is one
according to which these nebulae
contain
(at least) two distinct emission regions - one of "normal" Te (~
10000
K)
and chemical composition (~solar) and another of very low Te that is H-
deficient,
thus having high helium and metal abundances relative to hydrogen.
The
latter component emits strong He and heavy element ORLs but essentially
no
CELs.
The consistent picture that emerges from fitting a 2-component
photoionization
model to the spectroscopic data is that the H-poor component
is
in high-density inclusions, which provide only a minor fraction of the
total
nebular mass. We propose to directly detect these inclusions in the
planetary
nebula M 1-42 using WFPC2 (PC) to make a high spatial resolution
image
in the He I 5876 A ORL
and ratio it to Halpha. With NICMOS
(NIC1), we
plan
to observe the He I 10830 A line, which is substantially
collisionally
excited,
along with Palpha 18760 A. The ratio image of He I 10830 to Palpha is
expected
to be less likely to show the
inclusions, thus serving as an
important
control to the optical imaging. M 1-42 is one of the most extreme
cases
of the abundance and Te problem; it is reasonably bright and compact.
This
program has the potential to resolve a serious challenge to our current
understanding
of nebular astrophysics.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11186
Title:
Investigation
of the spatial and temporal structure of Europa's atmospheric emissisons
PI:
Joachim
Saur
PI
Institution:
Universitat
zu Koeln
We
propose to explore the spatial structure and temporal variability of
Europa's
O2 atmosphere with ACS/SBC. Previous HST images display non-uniform
UV
emission from Europa's atmosphere, which maximizes within the disk of
Europa
on its anti-Jovian northern quadrant. These images were taken at
western
elongation and are not conclusive,
but bring up the exciting question
whether
the non-uniform emission is due to a locally enhanced
neutral
atmosphere.
A locally inhomogeneous atmosphere would imply locally modified
surface properties. This might provide clues on
inhomogeneities of the
underlying
ice structure and thus properties of a
potential subsurface ocean.
Since
the inhomogeneous emission comes from within the disk of Europa, we
propose
to study Europa at eastern and western elongation to decide if the
locally
enhanced emission is truly an
atmospheric effect. We propose to take
for
each elongation five contiguous observations within one rotation period
of
Jupiter to discriminate between a competing effect that produces
inhomogeneous
emission patterns, i.e., the
electrodynamic interaction with
Jupiter's
magnetosphere. We will use ACS/SBC with PR130L prism to
completely
separate
the two prominent FUV oxygen lines OI 1304 A and OI 1356 A emitted
from
Europa's atmosphere.
======================================================================
Proposal
Category: GO
Scientific
Category: SOLAR SYSTEM
ID:
11187
Title:
A
Deep Search for Martian Dust Rings
PI:
Mark
Showalter
PI
Institution:
SETI
Institute
It
has been long suspected that Mars is encircled by two faint rings of
dust,
one
originating from each of its moons Phobos and Deimos. Similar dust rings
are
associated with many of the small, inner moons orbiting Jupiter, Saturn,
Uranus
and Neptune. On December 31, 2007, Earth will pass through Mars'
equatorial
plane just a week after its December 24 opposition, providing an
exceedingly
rare opportunity to image the rings under nearly ideal viewing
geometry.
The next equivalent viewing opportunity occurs in 2022. Using the
Wide
Fields of WFPC2 and a highly optimized observing plan, we expect to be
able
to detect rings with edge-on reflectivities of ~ 10^-8, which is at or
below
the level where most dynamicists expect rings to be visible. This is a
factor
of 10-30 more sensitive than the detection limit we achieved during a
slightly
inferior viewing opportunity in 2001. The rings have been predicted
to
show some interesting dynamical properties, including large asymmetries
and
inclinations.
A positive detection will test these predictions, serving as an
effective
test of dynamical models developed to account for the properties of
other
faint planetary rings as well. With such a stringent limit, even a
negative
result will be of considerable interest, challenging dynamicists to
explain
the remarkably low density of dust within the Martian system.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11188
Title:
First
Resolved Imaging of Escaping Lyman Continuum
PI:
Brian
Siana
PI
Institution:
Jet
Propulsion Laboratory
The
emission from star-forming galaxies appears to be responsible for
reionization
of the universe at z>6.
However, the models that attempt to
describe
the detailed impact of high-redshift galaxies on the surrounding
inter-galactic
medium (IGM) are strongly dependent upon several uncertain
parameters. Perhaps the most uncertain is the
fraction of HI-ionizing photons
produced
by young stars which escape into the IGM.
Most attempts to measure
this
"escape fraction" (f_esc) have produced null results.
Recently, a small
subset
of z~3 Lyman Break Galaxies (LBGs) has been found exhibiting large
escape
fractions. It remains unclear
however, what differentiates them from
other
LBGs. Several models attempt to
explain how such a large fraction of
ionizing
continuum can escape through the HI and dust in the ISM (eg.
"chimneys"
created by SNe winds, globular cluster formation, etc.), each
producing
unique signatures which can be observed with resolved imaging of the
escaping
Lyman continuum. We propose a
deep, high resolution WFPC2 image of
the
ionizing continuum (F336W) and the rest-frame 1500 Angstrom continuum
(F606W)
of five of the six known LBGs with large escape fractions.
These LBGs
all
fit within a single WFPC2 pointing, yielding high observing efficiency.
Additionally,
they all have z~3.1 or higher, the optimal redshift range for
probing
the Lyman Continuum region with available WFPC2 filters.
These
factors
make our proposed sample especially suitable for follow-up. With
these
data we will discern the mechanisms responsible for producing large
escape
fractions, and therefore gain insight into the process of reionization.
======================================================================
Proposal
Category: GO
Scientific
Category: COSMOLOGY
ID:
11189
Title:
Probing
the early universe with GRBs
PI:
Nial
Tanvir
PI
Institution:
University
of Leicester
Cosmology
is beginning to constrain the nature of the earliest stars and
galaxies
to form in the Universe, but direct observation of galaxies at z>6
remains
highly challenging due to their scarcity, intrinsically small size,
and
high luminosity distance. GRB
afterglows, thanks to their extreme
luminosities,
offer the possibility of circumventing these normal constraints
by
providing redshifts and spectral information which couldn't be obtained
through
direct observation of the host galaxies themselves.
In addition, the
association
of GRBs with massive stars means that they are an indicator of
star
formation, and that their hosts are likely responsible for a large
proportion
of the ionizing radiation during that era. Our
collaboration is
conducting
a campaign to rapidly identify and study candidate very high
redshift
bursts, bringing to bear a network of 2, 4 and 8m telescopes with
near-IR
instrumentation. Swift has proven
capable of detecting faint, distant
GRBs,
and reporting accurate positions for many bursts in near real-time.
Here
we propose to continue our HST program of targetting GRBs at z~6 and
above. HST is crucial to this endeavour,
allowing us (a) to characterise the
basic
properties, such as luminosity and colour, and in some cases
morphologies,
of the hosts, which is essential to understanding these
primordial
galaxies and their relationship to other galaxy populations; and
(b)
to monitor the late time afterglows and hence compare them to lower-z
bursts and test the use of GRBs as stan