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Daily Report #5194



 
 
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Old October 4th 10, 05:24 PM posted to sci.astro.hubble
Cooper, Joe
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Posts: 568
Default Daily Report #5194


HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5194

PERIOD COVERED: 8:00pm September 30 - 7:59pm October 3, 2010 (DOY 274/00:00z-276/23:59z)

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

Scheduled Successful
FGS GSAcq 23 23
FGS REAcq 24 24
OBAD with Maneuver 20 20

SIGNIFICANT EVENTS: (None)


OBSERVATIONS SCHEDULED:

ACS/WFC 12381

Imaging the Crab Nebula while it is Flaring in Gamma-rays

The high energy gamma-ray flux from the Crab nebula doubled in a
couple of days (from September 19 to September 21). Such enhancement,
never seen before, is clearly detected both by Agile and Fermi, the
two gamma-ray telescopes currently in operation. While such huge
brightening is exciting the entire astrophysical community, TOOs are
being scheduled by high energy space observatories such as Integral,
Swift and Chandra. By imaging the status of the knots and wisps in the
inner Crab nebula, HST could provide a unique piece of information,
which may yield a clue to understand the source behavior.

WFC3/UV 12348

WFC3/UVIS Charge Injection Test

In preparation for making charge injection (CI) available to
observers, this proposal will 1) confirm that the CI performs on-orbit
as it did on the ground, 2) provide an initial assessment of which CI
mode is most effective (10, 17, 25 line or continuous), and 3) obtain
a baseline calibration for each mode.

ACS/WFC 12310

LARS - The Lyman Alpha Reference Sample

Lyman-alpha (Lya) is intrinsically the strongest recombination line in
HII nebulae, reprocessing around 1/3 of the ionizing energy. This
fact, combined with a rest wavelength that makes it convenient for
high redshift studies have made Lya the dominant spectral probe of
galaxy formation and evolution in the distant universe. At the same
time, our understanding of emission and escape from galaxies is
extremely patchy, for two reasons: 1) The resonant nature of Lya makes
radiative transfer effects very important, and 2) with a rest
wavelength pretty far out in the ultra violet (UV), detailed studies
of local galaxies are difficult and require space instrumentation. In
contrast to the thousands of galaxies in the nearby universe that have
been studied at high spatial resolution (through ground based
telescopes and yet a little further with HST) in optical broad bands
and emission lines like H-alpha, only six (sic!) galaxies have Lya
imaging available.

The Lya images available so far indicate that when Lya escapes, it
does so primarily through a low surface brightness resonantly
scattered component. With this proposal, we aim at observing 14 new
targets and thereby increase the number of high resolution Lya images
to 20, for a UV and H-alpha selected sample. By utilizing an
alternative observational approach we will also improve the quality of
the images by an order of magnitude. A better physical understanding
of how Lya photons travel through and escape from galaxies is vital
for interpreting and understanding observations at high redshifts, and
would be an important legacy of HST in the JWST and ELT era, when the
high-resolution UV imaging window on the Universe has been closed.

WFC3/IR 12307

A public SNAPSHOT Survey of Gamma-ray Burst Host Galaxies

We propose to conduct a public infrared survey of the host galaxies of
Swift selected gamma-ray bursts (GRBs) at z3. By obtaining deep,
diffraction limited imaging in the IR we will complete detections for
the host galaxies, and in concert with our extensive ground based
afterglow and host programmes will compile a detailed catalog of the
properties of high-z galaxies selected by GRBs. In particular these
observations will enable us to study the colours, luminosities and
morphologies of the galaxies. This in turn informs studies of the
nature of the progenitors and the role of GRBs as probes of star
formation across cosmic history. Ultimately it provides a product of
legacy value which will greatly complement further studies with next
generation facilities such as ALMA and JWST.

COS/NUV/FUV/WFC3/UV 12248

How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and
Galactic Winds Below L*

One of the most vexing problems in galaxy formation concerns how gas
accretion and feedback influence the evolution of galaxies. In high
mass galaxies, numerical simulations predict the initial fuel is
accreted through 'cold' streams, after which AGN suppress star
formation to leave galaxies red and gas-poor. In the shallow potential
wells that host dwarf galaxies, gas accretion can be very efficient,
and "superwinds" driven either by hot gas expelled by SNe or momentum
imparted by SNe and hot-star radiation are regarded as the likely
source(s) of feedback. However, major doubts persist about the physics
of gas accretion, and particularly about SN-driven feedback, including
their scalings with halo mass and their influence on the evolution of
the galaxies. While "superwinds" are visible in X-rays near the point
of their departure, they generally drop below detectable
surface-brightness limits at ~ 10 kpc. Cold clumps in winds can be
detected as blue-shifted absorption against the galaxy's own
starlight, but the radial extent of these winds are difficult to
constrain, leaving their energy, momentum, and ultimate fate
uncertain. Wind prescriptions in hydrodynamical simulations are
uncertain and at present are constrained only by indirect
observations, e.g. by their influence on the stellar masses of
galaxies and IGM metallicity. All these doubts lead to one conclusion:
we do not understand gas accretion and feedback because we generally
do not observe the infall and winds directly, in the extended gaseous
halos of galaxies, when it is happening. To do this effectively, we
must harness the power of absorption-line spectroscopy to measure the
density, temperature, metallicity, and kinematics of small quantities
of diffuse gas in galaxy halos. The most important physical
diagnostics lie in the FUV, so this is uniquely a problem for HST and
COS. We propose new COS G130M and G160M observations of 41 QSOs that
probe the gaseous halos of 44 SDSS dwarf galaxies well inside their
virial radii. Using sensitive absorption-line measurements of the
multiphase gas diagnostics Lya, CII/IV, Si II/III/IV, and other
species, supplemented by optical data from SDSS and Keck, we will map
the halos of galaxies with L = 0.02 - 0.3 L*, stellar masses M* =
10^(8-10) Msun, over impact parameter from 15 - 150 kpc. These
observations will directly constrain the content and kinematics of
accreting and outflowing material, provide a concrete target for
simulations to hit, and statistically test proposed galactic superwind
models. These observations will also inform the study of galaxies at
high z, where the shallow halo potentials that host dwarf galaxies
today were the norm. These observations are low-risk and routine for
COS, easily schedulable, and promise a major advance in our
understanding of how dwarf galaxies came to be.

WFC3/UV 12229

HST U-band Survey of Star Clusters in Nearby Star-Forming Galaxies

We propose a small Snapshot program to obtain U-band imaging of a
sample of 22 nearby star-forming galaxies with existing HST B, V, and
I-band imaging. With the high UV efficiency and large field of view of
WFC3/UVIS, it is now possible to obtain deep U-band imaging for a
large sample of galaxies, and address fundamental questions on the
cluster systems which can only now be answered. We will focus mainly
on the young stellar cluster populations of these galaxies and use the
deep U-band observations to accurately age date tens or even hundreds
of clusters in each galaxy. By measuring the ages and masses of the
cluster populations, we will be able to answer many of the outstanding
questions regarding their properties, survival rates, cluster
formation histories and environmental dependencies. The overall aim
will be to relate cluster formation and cluster properties to the star
formation rates and morphologies of their host galaxies. In
particular, this dataset will be used to: 1) constrain the fraction of
stars that form in clusters and search for environmental dependencies;
2) study the cluster luminosity/mass function and determine if a
characteristic mass exists in the distribution; 3) measure the size
(radius) distribution of the clusters and determine if this has a
dependence on environment; 4) empirically constrain cluster disruption
laws; and 5) determine the star/cluster formation histories of these
galaxies over the past Gyr. This survey will complement existing
imaging and will provide a rich legacy dataset for the entire
community. We waive the 12 month proprietary period.

ACS/WFC 12209

A Strong Lensing Measurement of the Evolution of Mass Structure in
Giant Elliptical Galaxies

The structure and evolution of giant elliptical galaxies provide key
quantitative tests for the theory of hierarchical galaxy formation in
a cold dark matter dominated universe. Strong gravitational lensing
provides the only direct means for the measurement of individual
elliptical galaxy masses beyond the local universe, but there are
currently no large and homogeneous samples of strong lens galaxies at
significant cosmological look-back time. Hence, an accurate and
unambiguous measurement of the evolution of the mass-density structure
of elliptical galaxies has until now been impossible. Using
spectroscopic data from the recently initiated Baryon Oscillation
Spectroscopic Survey (BOSS) of luminous elliptical galaxies at
redshifts from approximately 0.4 to 0.7, we have identified a large
sample of high-probability strong gravitational lens candidates at
significant cosmological look-back time, based on the detection of
emission-line features from more distant galaxies along the same lines
of sight as the target ellipticals. We propose to observe 45 of these
systems with the ACS-WFC in order to confirm the incidence of lensing
and to measure the masses of the lens galaxies. We will complement
these lensing mass measurements with stellar velocity dispersions from
ground-based follow-up spectroscopy. In combination with similar data
from the Sloan Lens ACS (SLACS) Survey at lower redshifts, we will
directly measure the cosmic evolution of the ratio between lensing
mass and dynamical mass, to reveal the structural explanation for the
observed size evolution of elliptical galaxies (at high mass). We will
also measure the evolution of the logarithmic mass-density profile of
massive ellipticals, which is sensitive to the details of the merging
histories through which they are assembled. Finally, we will use our
lensing mass-to-light measurements to translate the BOSS galaxy
luminosity function into a mass function, and determine its evolution
in combination with data from the original Sloan Digital Sky Survey.

ACS/WFC 12166

A Snapshot Survey of The Most Massive Clusters of Galaxies

We propose the continuation of our highly successful HST/ACS SNAPshot
survey of a sample of 123 very X-ray luminous clusters in the redshift
range 0.3-0.7, detected and compiled by the MACS cluster survey. As
demonstrated by dedicated HST observations of the 12 most distant MACS
clusters (GO-09722) as well as by the MACS SNAPshots of an additional
25 obtained with ACS so far in Cycles 14 and 15, these systems
frequently exhibit strong gravitational lensing as well as spectacular
examples of violent galaxy evolution. A large number of additional
MACS SNAPs have since been obtained with WFPC2, leading to the
discovery of several more powerful cluster lenses. The dramatic loss,
however, of depth, field-of-view, and angular resolution compared to
ACS led to significantly reduced scientific returns, underlining the
need for ACS for this project. The proposed observations will provide
important constraints on the cluster mass distributions, on the
physical nature of ! galaxy-galaxy and galaxy-gas interactions in
cluster cores, and will yield a set of optically bright, lensed
galaxies for further 8-10m spectroscopy. For those of our targets with
existing ACS SNAPshot images, we propose SNAPshots in the WFC3 F110W
and F140W passbands to obtain colour information that will greatly
improve the secure identification of multiple-image systems and may,
in the form of F606W or F814W dropouts, lead to the lensing-enabled
discovery of very distant galaxies at z5. Acknowledging the broad
community interest in this sample (16 of the 25 targets of the
approved MCT cluster program are MACS discoveries) we waive our data
rights for these observations.

This proposal is an updated and improved version of our successful
Cycle 15 proposal of the same title. Alas, SNAP-10875 collected only
six snapshots in the F606W or F814W passbands, due to, first, a
clerical error at STScI which caused the program to be barred from
execution for four months and, ultimately, the failure of ACS. With
ACS restored, and WFC3 providing additional wavelength and redshift
leverage, we wish to resume this previously approved project.

COS/NUV 12041

COS-GTO: Io Atmosphere/STIS

We will use six HST orbits with COS to observe the disk-integrated
longitudinal distribution of Io's atmosphere, and ten HST orbits with
STIS to provide complementary disk-resolved information at key
locations. We will use the COS G225M grating to observe four SO2
absorption bands, which can be used to determine SO2 atmospheric
density. Disk-integrated 19 micron observations of the atmosphere
indicate that the anti-Jupiter hemisphere of Io has an atmospheric
density roughly ten times greater than the Jupiter-facing side
(Spencer et al. 2005), and mm-wave observations suggest a similar
pattern. However the infrared and mm-wave observations cannot easily
separate atmospheric density from atmospheric temperature, so these
results are model-dependent. Sparse 2100 2300 disk-resolved
observations (McGrath et al. 2000, Jessup et al. 2004) tell a
consistent story, but do not cover enough of Io's surface to provide
full confirmation of the long-wavelength result. We will therefore
observe Io's disk-integrated atmospheric density at six longitudes,
roughly 30, 90, 150, 210, 270, and 330 W, to confirm the 19 micron
results and improve our ability to model the 19-micron data. With
STIS, we plan disk-resolved 2000-3200 spectroscopy of Io's SO2
atmosphere. Our observations will target low-latitude regions away
from active plumes (in contrast to our Cycle 10 observations (Jessup
et al. 2004) which targeted the Prometheus plume), to look for the
effect of plumes on the atmosphere. We will also look at the variation
of low-latitude atmospheric abundance with terrain type, to look for
explanations for the large longitudinal variations in atmospheric
pressure to be studied with COS. Finally, we will look at a variety of
regions at two different times of day to determine the extent of
diurnal variations in the atmosphere, which are expected if the
atmosphere is dominantly supported by frost sublimation.

ACS/WFC 11996

CCD Daily Monitor (Part 3)

This program comprises basic tests for measuring the read noise and
dark current of the ACS WFC and for tracking the growth of hot pixels.
The recorded frames are used to create bias and dark reference images
for science data reduction and calibration. This program will be
executed four days per week (Mon, Wed, Fri, Sun) for the duration of
Cycle 17. To facilitate scheduling, this program is split into three
proposals. This proposal covers 308 orbits (19.25 weeks) from 21 June
2010 to 1 November 2010.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more
reliably removed from science data using darks taken with the same
exposure sequences as the science data, than with a single dark
current image scaled by desired exposure time. Therefore, dark current
images must be collected using all sample sequences that will be used
in science observations. These observations will be used to monitor
changes in the dark current of the WFC3-IR channel on a day-to-day
basis, and to build calibration dark current ramps for each of the
sample sequences to be used by Gos in Cycle 17. For each sample
sequence/array size combination, a median ramp will be created and
delivered to the calibration database system (CDBS).

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the
UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.
Initially found via an unexpected bowtie- shaped feature in flatfield
ratios, subsequent lab tests on similar e2v devices have since shown
that it is also present as simply an overall offset across the entire
CCD, i.e., a QE offset without any discernable pattern. These lab
tests have further revealed that overexposing the detector to count
levels several times full well fills the traps and effectively
neutralizes the bowtie. Each visit in this proposal acquires a set of
three 3x3 binned internal flatfields: the first unsaturated image will
be used to detect any bowtie, the second, highly exposed image will
neutralize the bowtie if it is present, and the final image will allow
for verification that the bowtie is gone.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set
of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K
subarray biases are acquired at less frequent intervals throughout the
cycle to support subarray science observations. The internals from
this proposal, along with those from the anneal procedure (Proposal
11909), will be used to generate the necessary superbias and superdark
reference files for the calibration pipeline (CDBS).

COS/NUV 11900

NUV Internal/External Wavelength Scale Monitor

This program monitors the offsets between the wavelength scale set by
the internal wavecal versus that defined by absorption lines in
external targets. This is accomplished by observing two external
radial velocity standard targets: HD187691 with G225M and G285M and
HD6655 with G285M and G230L. The two standard targets have little flux
in the wavelength range covered by G185M and so Feige 48 (sdO) is
observed with this grating. Both Feige 48 and HD6655 are also observed
in SMOV. The cenwaves observed in this program are a subset of the
ones used during Cycle 17. Observing all cenwaves would require a
considerably larger number of orbits. Constraints on scheduling of
each target are placed so that each target is observed once every ~2-3
months. Observing the three targets every month would also require a
considerably larger number of orbits.

WFC3/ACS/UVIS 11877

HST Cycle 17 and Post-SM4 Optical Monitor

This program is the Cycle 17 implementation of the HST Optical
Monitoring Program.

The 36 orbits comprising this proposal will utilize ACS (Wide Field
Channel) and WFC3 (UVIS Channel) to observe stellar cluster members in
parallel with multiple exposures over an orbit. Phase retrieval
performed on the PSF in each image will be used to measure primarily
focus, with the ability to explore apparent coma, and astigmatism
changes in WFC3.

The goals of this program are to: 1) monitor the overall OTA focal
length for the purposes of maintaining focus within science tolerances
2) gain experience with the relative effectiveness of phase retrieval
on WFC3/UVIS PSFs 3) determine focus offset between the imagers and
identify any SI-specific focus behavior and dependencies

If need is determined, future visits will be modified to interleave
WFC3/IR channel and STIS/CCD focii measurements.

STIS/CCD 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,
and 1x1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

COS/NUV/FUV 11728

The Impact of Starbursts on the Gaseous Halos of Galaxies

Perhaps the most important (yet uncertain) aspects of galaxy evolution
are the processes by which galaxies accrete gas and by which the
resulting star formation and black hole growth affects this accreting
gas. It is believed that both the form of the accretion and the nature
of the feedback change as a function of the galaxy mass. At low mass
the gas comes in cold and the feedback is provided by massive stars.
At high mass, the gas comes in hot, and the feedback is from an AGN.
The changeover occurs near the mass where the galaxy population
transitions from star-forming galaxies to red and dead ones. The
population of red and dead galaxies is building with cosmic time, and
it is believed that feedback plays an important role in this process:
shutting down star formation by heating and/or expelling the reservoir
of cold halo gas. To investigate these ideas, we propose to use COS
far-UV spectra of background QSOs to measure the properties of the
halo gas in a sample of galaxies near the transition mass that have
undergone starbursts within the past 100 Myr to 1 Gyr. The galactic
wind associated with the starburst is predicted to have affected the
properties of the gaseous halo. To test this, we will compare the
properties of the halos of the post-starburst galaxies to those of a
control sample of galaxies matched in mass and QSO impact parameter.
Do the halos of the post-starburst galaxies show a higher incidence
rate of Ly-Alpha and metal absorption-lines? Are the kinematics of the
halo gas more disturbed in the post-starbursts? Has the wind affected
the ionization state and/or the metallicity of the halo? These data
will provide fresh new insights into the role of feedback from massive
stars on the evolution of galaxies, and may also offer clues about the
properties of the QSO metal absorption-line systems at high-redshift .

WFC3/IR 11696

Infrared Survey of Star Formation Across Cosmic Time

We propose to use the unique power of WFC3 slitless spectroscopy to
measure the evolution of cosmic star formation from the end of the
reionization epoch at z6 to the close of the galaxy-building era at
z~0.3.Pure parallel observations with the grisms have proven to be
efficient for identifying line emission from galaxies across a broad
range of redshifts. The G102 grism on WFC3 was designed to extend this
capability to search for Ly-alpha emission from the first galaxies.
Using up to 250 orbits of pure parallel WFC3 spectroscopy, we will
observe about 40 deep (4-5 orbit) fields with the combination of G102
and G141, and about 20 shallow (2-3 orbit) fields with G141 alone.

Our primary science goals at the highest redshifts a (1) Detect Lya
in ~100 galaxies with z5.6 and measure the evolution of the Lya
luminosity function, independent of of cosmic variance; 2) Determine
the connection between emission line selected and continuum-break
selected galaxies at these high redshifts, and 3) Search for the
proposed signature of neutral hydrogen absorption at re-ionization. At
intermediate redshifts we will (4) Detect more than 1000 galaxies in
Halpha at 0.5z1.8 to measure the evolution of the
extinction-corrected star formation density across the peak epoch of
star formation. This is over an order-of-magnitude improvement in the
current statistics, from the NICMOS Parallel grism survey. (5) Trace
``cosmic downsizing" from 0.5z2.2; and (6) Estimate the evolution in
reddening and metallicty in star-forming galaxies and measure the
evolution of the Seyfert population. For hundreds of spectra we will
be able to measure one or even two line pair ratios -- in particular,
the Balmer decrement and [OII]/[OIII] are sensitive to gas reddening
and metallicity. As a bonus, the G102 grism offers the possibility of
detecting Lya emission at z=7-8.8.

To identify single-line Lya emitters, we will exploit the wide
0.8--1.9um wavelength coverage of the combined G102+G141 spectra. All
[OII] and [OIII] interlopers detected in G102 will be reliably
separated from true LAEs by the detection of at least one strong line
in the G141 spectrum, without the need for any ancillary data. We
waive all proprietary rights to our data and will make high-level data
products available through the ST/ECF.

WFC3/IR 11694

Mapping the Interaction Between High-Redshift Galaxies and the
Intergalactic Environment

With the commissioning of the high-throughput large-area camera
WFC3/IR, it is possible for the first time to undertake an efficient
survey of the rest-frame optical morphologies of galaxies at the peak
epoch of star formation in the universe. We therefore propose deep
WFC3/IR imaging of over 320 spectroscopically confirmed galaxies
between redshift 1.6 z 3.4 in well-studied fields which lie along
the line of sight to bright background QSOs. The spectra of these
bright QSOs probe the IGM in the vicinity of each of the foreground
galaxies along the line of sight, providing detailed information on
the physical state of the gas at large galactocentric radii. In
combination with our densely sampled UV/IR spectroscopy, stellar
population models, and kinematic data in these fields, WFC3/IR imaging
data will permit us to construct a comprehensive picture of the
structure, dynamics, and star formation properties of a large
population of galaxies in the early universe and their effect upon
their cosmological environment.

ACS/WFC/WFC3/UV/IR 11691

Using Massive Star Clusters in Merger Remnants To Provide Reference
Colors of Intermediate-Age Stellar Populations

Much current research in cosmology and galaxy formation relies on an
accurate interpretation of colors of galaxies in terms of their
evolutionary state, i.e., in terms of ages and metallicities. One
particularly important topic is the ability to identify early-type
galaxies at "intermediate" ages (~ 500 Myr - 5 Gyr), i.e., the period
between the end of star formation and ~ half the age of the universe.
Currently, integrated-light studies must rely on population synthesis
models which rest upon spectral libraries of stars in the solar
neighborhood. These models have a difficult time correctly
incorporating short-lived evolutionary phases such as thermally
pulsing AGB stars, which produce up to 80% of the flux in the near-IR
in this age range. Furthermore, intermediate-age star clusters in the
Local Group do not represent proper templates against which to
calibrate population synthesis models in this age range, because their
masses are too low to render the effect of stochastic fluctuations due
to the number of bright RGB and AGB stars negligible. As a
consequence, current population synthesis models have trouble
reconciling the evolutionary state of high-redshift galaxies from
optical versus near-IR colors. We propose a simple and effective
solution to this issue, namely obtaining high-quality EMPIRICAL colors
of massive globular clusters in galaxy merger remnants which span this
important age range. These colors should serve as relevant references,
both to identify intermediate-age objects in the local and distant
universe and as calibrators for population synthesis modelers.

WFC3/ACS/IR 11677

Is 47 Tuc Young? Measuring its White Dwarf Cooling Age and Completing
a Hubble Legacy

With this proposal we will firmly establish the age of 47 Tuc from its
cooling white dwarfs. 47 Tuc is the nearest and least reddened of the
metal-rich disk globular clusters. It is also the template used for
studying the giant branches of nearby resolved galaxies. In addition,
the age sensitive magnitude spread between the main sequence turnoff
and horizontal branch is identical for 47 Tuc, two bulge globular
clusters and the bulge field population. A precise relative age
constraint for 47 Tuc, compared to the halo clusters M4 and NGC 6397,
both of which we recently dated via white dwarf cooling, would
therefore constrain when the bulge formed relative to the old halo
globular clusters. Of particular interest is that with the higher
quality ACS data on NGC 6397, we are now capable with the technique of
white dwarf cooling of determining ages to an accuracy of +/-0.4 Gyrs
at the 95% confidence level. Ages derived from the cluster turnoff are
not currently capable of reaching this precision. The important role
that 47 Tuc plays in galaxy formation studies, and as the metal-rich
template for the globular clusters, makes the case for a white dwarf
cooling age for this metal-rich cluster compelling.

Several recent analyses have suggested that 47 Tuc is more than 2 Gyrs
younger than the Galactic halo. Others have suggested an age similar
to that of the most metal poor globular clusters. The current
situation is clearly uncertain and obviously a new approach to age
dating this important cluster is required.

With the observations of 47 Tuc, this project will complete a legacy
for HST. It will be the third globular cluster observed for white
dwarf cooling; the three covering almost the full metallicity range of
the cluster system. Unless JWST has its proposed bluer filters (700
and 900 nm) this science will not be possible perhaps for decades
until a large optical telescope is again in space. Ages for globular
clusters from the main sequence turnoff are less precise than those
from white dwarf cooling making the science with the current proposal
truly urgent.

WFC3/UVIS/IR 11644

A Dynamical-Compositional Survey of the Kuiper Belt: A New Window Into
the Formation of the Outer Solar System

The eight planets overwhelmingly dominate the solar system by mass,
but their small numbers, coupled with their stochastic pasts, make it
impossible to construct a unique formation history from the dynamical
or compositional characteristics of them alone. In contrast, the huge
numbers of small bodies scattered throughout and even beyond the
planets, while insignificant by mass, provide an almost unlimited
number of probes of the statistical conditions, history, and
interactions in the solar system. To date, attempts to understand the
formation and evolution of the Kuiper Belt have largely been dynamical
simulations where a hypothesized starting condition is evolved under
the gravitational influence of the early giant planets and an attempt
is made to reproduce the current observed populations. With little
compositional information known for the real Kuiper Belt, the test
particles in the simulation are free to have any formation location
and history as long as they end at the correct point. Allowing
compositional information to guide and constrain the formation,
thermal, and collisional histories of these objects would add an
entire new dimension to our understanding of the evolution of the
outer solar system. While ground based compositional studies have hit
their flux limits already with only a few objects sampled, we propose
to exploit the new capabilities of WFC3 to perform the first ever
large-scale dynamical-compositional study of Kuiper Belt Objects
(KBOs) and their progeny to study the chemical, dynamical, and
collisional history of the region of the giant planets. The
sensitivity of the WFC3 observations will allow us to go up to two
magnitudes deeper than our ground based studies, allowing us the
capability of optimally selecting a target list for a large survey
rather than simply taking the few objects that can be measured, as we
have had to do to date. We have carefully constructed a sample of 120
objects which provides both overall breadth, for a general
understanding of these objects, plus a large enough number of objects
in the individual dynamical subclass to allow detailed comparison
between and within these groups. These objects will likely define the
core Kuiper Belt compositional sample for years to come. While we have
many specific results anticipated to come from this survey, as with
any project where the field is rich, our current knowledge level is
low, and a new instrument suddenly appears which can exploit vastly
larger segments of the population, the potential for discovery -- both
anticipated and not -- is extraordinary.

WFC3/UV 11605

Obtaining the Missing Links in the Test of Very Low Mass Evolutionary
Models with HST

We are proposing for spatially resolved ACS+HRC observations of 11
very low mass binaries spanning late-M, L and T spectral types in
order to obtain precise effective temperature measurements for each
component. All of our targets are part of a program in which we are
measuring dynamical masses of very low-mass binaries to an
unprecedented precision of 10% (or better). However, without precise
temperature measurements, the full scientific value of these mass
measurements cannot be realized. Together, mass and temperature
measurements will allow us to distinguish between brown dwarf
evolutionary models that make different assumptions about the interior
and atmospheric structure of these ultra-cool objects. While dynamical
masses can be obtained from the ground in the near-IR, obtaining
precise temperatures require access to optical data which, for these
sub-arcsecond binaries, can only be obtained from space with Hubble.

COS/NUV/FUV 11598

How Galaxies Acquire their Gas: A Map of Multiphase Accretion and
Feedback in Gaseous Galaxy Halos

We propose to address two of the biggest open questions in galaxy
formation - how galaxies acquire their gas and how they return it to
the IGM - with a concentrated COS survey of diffuse multiphase gas in
the halos of SDSS galaxies at z = 0.15 - 0.35. Our chief science goal
is to establish a basic set of observational facts about the physical
state, metallicity, and kinematics of halo gas, including the sky
covering fraction of hot and cold material, the metallicity of infall
and outflow, and correlations with galaxy stellar mass, type, and
color - all as a function of impact parameter from 10 - 150 kpc.
Theory suggests that the bimodality of galaxy colors, the shape of the
luminosity function, and the mass-metallicity relation are all
influenced at a fundamental level by accretion and feedback, yet these
gas processes are poorly understood and cannot be predicted robustly
from first principles. We lack even a basic observational assessment
of the multiphase gaseous content of galaxy halos on 100 kpc scales,
and we do not know how these processes vary with galaxy properties.
This ignorance is presently one of the key impediments to
understanding galaxy formation in general. We propose to use the
high-resolution gratings G130M and G160M on the Cosmic Origins
Spectrograph to obtain sensitive column density measurements of a
comprehensive suite of multiphase ions in the spectra of 43 z 1 QSOs
lying behind 43 galaxies selected from the Sloan Digital Sky Survey.
In aggregate, these sightlines will constitute a statistically sound
map of the physical state and metallicity of gaseous halos, and
subsets of the data with cuts on galaxy mass, color, and SFR will seek
out predicted variations of gas properties with galaxy properties. Our
interpretation of these data will be aided by state-of-the-art
hydrodynamic simulations of accretion and feedback, in turn providing
information to refine and test such models. We will also use Keck,
MMT, and Magellan (as needed) to obtain optical spectra of the QSOs to
measure cold gas with Mg II, and optical spectra of the galaxies to
measure SFRs and to look for outflows. In addition to our other
science goals, these observations will help place the Milky Way's
population of multiphase, accreting High Velocity Clouds (HVCs) into a
global context by identifying analogous structures around other
galaxies. Our program is designed to make optimal use of the unique
capabilities of COS to address our science goals and also generate a
rich dataset of other absorption-line systems.

STIS/CCD 11572

Characterizing Atmospheric Sodium in the Transiting Hot-Jupiter
HD189733b

We propose STIS transit observations of the exoplanet HD189733b with
the goal of measuring atmospheric atomic sodium. Our strategy is to
repeat the observing methods used for HD209458b, which resulted in a
successful exoplanetary atmospheric sodium detection. Initial
ground-based measurements suggest that the sodium signature on
HD189733 could be up to three times larger than HD209458b, making a
robust 8 detection possible within a 12 orbit program observing three
transits. Transit transmission spectra resulting from space- based
measurements have the advantage of retaining absolute transit depths
when features are measured, which will make it possible to provide an
observational link between sodium and atmospheric haze detected with
ACS. Such a link can break modeling degeneracies and providing
stringent constraints on the overall atmospheric properties, making
such atmospheric information as abundances and the
temperature-pressure-altitude relation known. A successful measurement
will also allow for comparative atmospheric exoplanetology, as an
atmospheric feature will be measured with the same instrument in two
separate planets.


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