HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5184
PERIOD
COVERED: 5am September 17 - 5am September 20, 2010 (DOY 260/09:00z-263/09:00z)
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
12416
- GSAcq(1,2,1) at 263/5:25:24z and REAcq(1,2,1) at 263/06:57:58z and
REAcq(1,2,1)
at 263/08:33:54z all failed due to search radius limit exceeded.
Observations affected, COS 3-6 Proposal ID#11728; WFC3 5-10
Proposal ID#11700
COMPLETED
OPS REQUEST:
18918-0
Uplink new FGS calibration tables @ 262/23:32z
18921-0
R/T OBAD to Correct Attitude Error @ 263/06:32z
COMPLETED
OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS
GSAcq
19
18
FGS
REAcq
21
19
OBAD
with Maneuver 15 15
SIGNIFICANT
EVENTS:
The
FGS distortion and Calibration tables were successfully uplinked at
262/23:30z.
Table dumps performed showed the expected changes for the
FGS-2R2
values being modified. The first guide star acquisition at
263/01:30z
performed nominally.
FGS
12320
The
Ages of Globular Clusters and the Population II Distance Scale
Globular
clusters are the oldest objects in the universe whose age can
be
accurately determined. The dominant error in globular cluster age
determinations
is the uncertain Population II distance scale. We propose
to
use FGS 1r to obtain parallaxes with an accuracy of 0.2
milliarcsecond
for 9 main sequence stars with [Fe/H] < -1.5. This will
determine
the absolute magnitude of these stars with accuracies of 0.04
to
0.06mag. This data will be used to determine the distance to 24
metal-poor
globular clusters using main sequence fitting. These
distances
(with errors of 0.05 mag) will be used to determine the ages
of
globular clusters using the luminosity of the subgiant branch as an
age
indicator. This will yield absolute ages with an accuracy 5%, about
a
factor of two improvement over current estimates. Coupled with
existing
parallaxes for more metal-rich stars, we will be able to
accurately
determine the age for globular clusters over a wide range of
metallicities
in order to study the early formation history of the Milky
Way
and provide an independent estimate of the age of the universe.
The
Hipparcos database contains only 1 star with [Fe/H] < -1.4 and an
absolute
magnitude error less than 0.18 mag which is suitable for use in
main
sequence fitting. Previous attempts at main sequence fitting to
metal-poor
globular clusters have had to rely on theoretical
calibrations
of the color of the main sequence. Our HST parallax program
will
remove this source of possible systematic error and yield distances
to
metal-poor globular clusters which are significantly more accurate
than
possible with the current parallax data. The HST parallax data will
have
errors which are 10 times smaller than the current parallax data.
Using
the HST parallaxes, we will obtain main sequence fitting distances
to
11 globular clusters which contain over 500 RR Lyrae stars. This will
allow
us to calibrate the absolute magnitude of RR Lyrae stars, a
commonly
used Population II distance indicator.
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 z<3. 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.
ACS/WFC
12292
SWELLS:
Doubling the Number of Disk-dominated Edge-on Spiral Lens
Galaxies
The
formation of realistic disk galaxies within the LCDM cosmology is
still
largely an unsolved problem. Theory is now beginning to make
predictions
for how dark matter halos respond to galaxy formation, and
for
the properties of disk galaxies. Measuring the density profiles of
dark
matter halos on galaxy scales is therefore a strong test for the
standard
paradigm of galaxy formation, offering great potential for
discovery.
However, the degeneracy between the stellar and dark matter
contributions
to galaxy rotation curves remains a major obstacle. Strong
gravitational
lensing, when combined with spatially resolved kinematics
and
stellar population models, can solve this long-standing problem.
Unfortunately,
this joint methodology could not be exploited until
recently
due to the paucity of known edge-on spiral lenses. We have
developed
and demonstrated an efficient technique to find exactly these
systems.
During supplemental cycle-16 we discovered five new spiral lens
galaxies,
suitable for rotation curve measurements. We propose
multi-color
HST imaging of 16 candidates and 2 partially-imaged
confirmed
systems, to measure a sample of eight new edge-on spiral
lenses.
This program will at least double the number of known
disk-dominated
systems. This is crucial for constraining the relative
contribution
of the disk, bulge and dark halo to the total density
profile.
WFC3/IR
12265
Determining
the Physical Nature of a Unique Giant Lya Emitter at z=6.595
We
propose deep WFC3/IR imaging for a giant Lya emitter (LAE) with a
Keck
spectroscopic redshift of z=6.595 discovered by extensive
narrow-band
imaging with Subaru in the SXDS-UKIDSS/UDS field. This
remarkable
object is unique in many respects including its large stellar
mass
and luminous nebula which extends over 17 kpc; no equivalent source
has
been found in other surveys. The nature of this rare object is
unclear.
Fundamental to progress is determining the origin of star
formation
in such an early massive object; if the age of the stellar
population
is short we are likely witnessing a special moment in the
formation
history of a massive galaxy. The heating source for the nebula
is
also unclear; options include intense star formation, the infall of
cold
gas onto a dark halo or shock heating from a merger. We will take
deep
broad-band (F125W and F160W) images and an intermediate-band
(F098M)
image which will be analyzed in conjunction with ultra-deep IRAC
3.6
and 4.5 micron data being taken by the Spitzer/SEDS project. These
data
will enable us to constrain the star formation rate and stellar
age.
Moreover, the UV continuum morphology and Lya-line distribution
will
be investigated for evidence of a major merger, cold accretion, or
hot
bubbles associated with outflows. We will address the physical
origin
of the remarkable object observed at an epoch where massive
galaxies
are thought to begin their assembly.
WFC3/UV/IR
12234
Differentiation
in the Kuiper belt: a Search for Silicates on Icy
Bodies.
We
currently have a large on-going program (Go Program 11644, 120
orbits)
to exploit the superb stability and photometric characteristics
of
HST and the broad range in wavelength coverage of the WFC3 to make
broad-band
vis/IR spectral observations of a large sample of Kuiper belt
objects.
Though the survey is currently only ~50% complete, the quality
and
unprecedented signal-to-noise of these observations has revealed the
existence
of a previously undiscovered spectral variability not
explainable
within our current understanding of these objects.
A
possible explanation for this variability is that with this faint set
of
Kuiper belt objects, we are beginning to see the difference between
larger
differentiated objects and smaller non-differentiated objects.
Its
seems that the small and likely undifferentiated objects are
exhibiting
silicate features that affect our photometry - features not
exhibited
by the icy mantles of larger icy bodies.
We
propose a small add-on survey to dramatically increase the scientific
results
of our large program. The proposed observations will use the
proven
capabilities of WFC3 to make broad and narrow-band photometric
observations
to detect spectral features in the 1.0-1.3 micron range of
a
small subset of our sources. The 13 targets have been carefully
selected
to cover the range of spectral variability detected in our
large
program as well as sample the entire dynamical range and physical
sizes
of these targets. These observations will allow the identification
of
undifferentiated Kuiper belt objects by detection of their silicate
features.
As a probe for differentiation, these observations could
constrain
the natal locations of different Kuiper belt classes, a
constraint
currently unavailable to formation models. This small set of
observations
will allow the calibration of the spectral variability seen
in
our large program, and drastically enhance the scientific output of
our
full Cycle 17 sample.
ACS/WFC
12210
SLACS
for the Masses: Extending Strong Lensing to Lower Masses and
Smaller
Radii
Strong
gravitational lensing provides the most accurate possible
measurement
of mass in the central regions of early-type galaxies
(ETGs).
We propose to continue the highly productive Sloan Lens ACS
(SLACS)
Survey for strong gravitational lens galaxies by observing a
substantial
fraction of 135 new ETG gravitational-lens candidates with
HST-ACS
WFC F814W Snapshot imaging. The proposed target sample has been
selected
from the seventh and final data release of the Sloan Digital
Sky
Survey, and is designed to complement the distribution of previously
confirmed
SLACS lenses in lens-galaxy mass and in the ratio of Einstein
radius
to optical half-light radius. The observations we propose will
lead
to a combined SLACS sample covering nearly two decades in mass,
with
dense mapping of enclosed mass as a function of radius out to the
half-light
radius and beyond. With this longer mass baseline, we will
extend
our lensing and dynamical analysis of the mass structure and
scaling
relations of ETGs to galaxies of significantly lower mass, and
directly
test for a transition in structural and dark-matter content
trends
at intermediate galaxy mass. The broader mass coverage will also
enable
us to make a direct connection to the structure of well-studied
nearby
ETGs as deduced from dynamical modeling of their line-of-sight
velocity
distribution fields. Finally, the combined sample will allow a
more
conclusive test of the current SLACS result that the intrinsic
scatter
in ETG mass-density structure is not significantly correlated
with
any other galaxy observables. The final SLACS sample at the
conclusion
of this program will comprise approximately 130 lenses with
known
foreground and background redshifts, and is likely to be the
largest
confirmed sample of strong-lens galaxies for many years to come.
COS/FUV
12169
The
Frequency and Chemical Composition of Planetary Debris Discs around
Young
White Dwarfs
Throughout
the past few years, it has become increasingly clear that the
most
plausible scenario to explain the metal-pollution observed in ~20%
of
all cool white dwarfs is accretion from rocky debris material -
suggesting
that these white dwarfs may have had, or may still have
terrestial
planets as well. This hypothesis is corroborated through the
infrared
detection of circumstellar dust around the most heavily
polluted
white dwarfs. Traditionally, the detection of metal pollution
is
done in the optical using the Ca H/K lines, leading to a strong bias
against
hot/young white dwarfs. Hence, most of our knowledge about the
late
evolution of planetary systems is based on white dwarfs with
cooling
ages >0.5Gyr. We propose an HST/COS ultraviolet spectroscopic
snapshot
survey to carry out the first systematic investigation of the
fraction
of metal-pollution among young (20-100Myr) white dwarfs,
probing
the correlation with white dwarf (and hence progenitor) mass,
and
determining the Si/H, C/H, and potentially N/H and O/H abundance
ratios
of their circumstellar debris material.
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 z>5. 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/FUV
12084
G140L/1280
Internal to External Wavelength Scale
This
program observes NGC330-B37 to determine the offsets between the
PSA
and WCA wavelength scales (for FP-POS=3) for the new G140L/1280 mode
that
will be available starting in Cycle 18. The results of the analysis
of
these data will be used to update the FUV wavelength dispersion
reference
file.
In
addition since it this the first time that this mode is used, both on
on-orbit
or on the ground, we obtain also data at FP-POS=1 and 4 which
inform
us of the extremes of the wavelength range that can be seen with
G140L/1280.
Note
that this program can only be executed after FSW changes occur
(current
estimate for these FSW changes is ~Aug 2010 timeframe) since
this
mode in not yet implemented.
COS/NUV/FUV
12080
COS
G140L Optics Alignment and Focus
A
G140L focus sweep will be performed using the B2Ia star AZV18 in the
Small
Magellanic Cloud. A sequence of time-tag spectra will be acquired
through
the PSA aperture (CENWAVE=1105 A), at a range of focus settings.
There
will be 17 focus settings sampled, ranging from -800 to +800 in
100-step
intervals. The optimum focus will be determined by
cross-correlating
prominent absorption features in the spectra with a
template
high resolution STIS E140M spectrum, then choosing the focus
setting
yielding the narrowest cross-correlation profile from the
sequence.
This is similar to the focusing procedure used for the G140L
grating
during SMOV (PID 11484, Visit 3), except that the new focus
sweep
will extend to more extreme focus positions around 0 (+/-800
instead
of +/-600). The inclusion of additional focus positions is
necessary
because the G140L focus curve from SMOV (cross-correlation
FWHM
vs. focus position) is broad and shallow, making it difficult to
measure
the minimum in the curve. After obtaining an exposure at the
most
extreme positive focus position (+800), the focus is returned to
its
nominal position (0). A final spectrum is then acquired at that
position,
for repeatability comparison with the earlier FOCUS=0
spectrum.
After the data are analyzed, a patchable constant SMS update
of
OSM1 focus for the G140L grating will be uplinked.
WFC3/UV
12019
After
the Fall: Fading AGN in Post-starburst Galaxies
We
propose joint Chandra and HST observations of an extraordinary sample
of
12 massive post-starburst galaxies at z=0.4-0.8 that are in the
short-lived
evolution phase a few 100 Myr after the peak of
merger-driven
star formation and AGN activity. We will use the data to
measure
X-ray luminosities, black hole masses, and accretion rates; and
with
the accurate "clocks" provided by post-starburst stellar
populations,
we will directly test theoretical models that predict a
power-law
decay in the AGN light curve. We will also test whether star
formation
and black hole accretion shut down in lock-step, quantify
whether
the black holes transition to radiatively inefficient accretion
states,
and constrain the observational signatures of black hole
mergers.
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/IR
11909
UVIS
Hot Pixel Anneal
The
on-orbit radiation environment of WFC3 will continually generate new
hot
pixels. This proposal performs the procedure required for repairing
those
hot pixels in the UVIS CCDs. During an anneal, the two-stage
thermo-electric
cooler (TEC) is turned off and the four-stage TEC is
used
as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of
the
CCD warmup, a majority of the hot pixels will be fixed; previous
instruments
such as WFPC2 and ACS have seen repair rates of about 80%.
Internal
UVIS exposures are taken before and after each anneal, to allow
an
assessment of the procedure's effectiveness in WFC3, provide a check
of
bias, global dark current, and hot pixel levels, as well as support
hysteresis
(bowtie) monitoring and CDBS reference file generation. One
IR
dark is taken after each anneal, to provide a check of the IR
detector.
WFC3/UVIS
11907
UVIS
Cycle 17 Contamination Monitor
The
UV throughput of WFC3 during Cycle 17 is monitored via weekly
standard
star observations in a subset of key filters covering 200-600nm
and
F606W, F814W as controls on the red end. The data will provide a
measure
of throughput levels as a function of time and wavelength,
allowing
for detection of the presence of possible contaminants.
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
11896
NUV
Spectroscopic Sensitivity Monitoring
The
purpose of this proposal is to monitor sensitivity of each NUV
grating
mode to detect any changes due to contamination or other causes.
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.
ACS/WFC3
11734
The
Hosts of High Redshift Gamma-Ray Bursts
Gamma-ray
bursts are the most luminous explosive events known, acting as
beacons
to the high redshift universe. Long duration GRBs have their
origin
in the collapse of massive stars and thus select star forming
galaxies
across a wide range of redshift. Due to their bright afterglows
we
can study the details of GRB host galaxies via absorption
spectroscopy,
providing redshifts, column densities and metallicities
for
galaxies far too faint to be accessible directly with current
technology.
We have already obtained deep ground based observations for
many
hosts and here propose ACS/WFC3 and WFC3 observations of the fields
of
bursts at z>3 which are undetected in deep ground based images. These
observations
will study the hosts in emission, providing luminosities
and
morphologies and will enable the construction of a sample of high-z
galaxies
with more detailed physical properties than has ever been
possible
before.
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 z>6 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 are: (1) Detect Lya
in
~100 galaxies with z>5.6 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 0.5<z<1.8 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
0.5<z<2.2;
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/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.
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.
WFC3/IR
11591
Are
Low-Luminosity Galaxies Responsible for Cosmic Reionization?
Our
group has demonstrated that massive clusters, acting as powerful
cosmic
lenses, can constrain the abundance and properties of
low-luminosity
star-forming sources beyond z~6; such sources are thought
to
be responsible for ending cosmic reionization. The large
magnification
possible in the critical regions of well-constrained
clusters
brings sources into view that lie at or beyond the limits of
conventional
exposures such as the UDF. We have shown that the
combination
of HST and Spitzer is particularly effective in delivering
the
physical properties of these distant sources, constraining their
mass,
age and past star formation history. Indirectly, we therefore gain
a
valuable glimpse to yet earlier epochs. Recognizing the result (and
limitations)
of blank field surveys, we propose a systematic search
through
10 lensing clusters with ACS/F814W and WFC3/[F110W+F160W] (in
conjunction
with existing deep IRAC data). Our goal is to measure with
great
accuracy the luminosity function at z~7 over a range of at least 3
magnitude,
based on the identification of about 50 lensed galaxies at
6.5<z<8.
Our survey will mitigate cosmic variance and extend the search
both
to lower luminosities and, by virtue of the WFC3/IRAC combination,
to
higher redshift. Thanks to the lensing amplification spectroscopic
follow-up
will be possible and make our findings the most robust prior
to
the era of JWST and the ELTs.