HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5067
PERIOD
COVERED: 5am April 2 - 5am April 5, 2010 (DOY 092/09:00z-095/09:00z)
OBSERVATIONS
SCHEDULED
WFC3/IR/S/C
12097
Additional
IR Subarray Dark Current Measurements (in support of GO
programs
11205, 11580)
This
proposal will produce IR dark images necessary to calibrate GO
science
observations (already taken, see proposals 11205 and 11580) that
use
observing modes not supported by the existing IR dark current
monitor
(proposal 11929). These modes are as follows: SQ256SUB/SPARS100,
SQ256SUB/SPARS200,
SQ512SUB/SPARS10, SQ512SUB/SPARS100, and
SQ512SUB/SPARS200.
WFC3/IR
12088
Tungsten
lamp warm-up time
The
purpose of this proposal is to determine the time required for the
primary
UVIS & IR tungsten lamps to fully warm up and output to
stabilize.
WFC3/UV
12077
Monitoring
the Aftermath of an Asteroid Impact Event
Our
Director's Discretionary program (GO-12053) to image the newly
discovered
object P/2010 A2 executed successfully on 2010 Jan 25 and 29
with
spectacular results. Hubble has apparently borne witness to the
first
detection of a collision in the asteroid belt. Hubble imaging with
the
WFC3 has revealed an object unlike anything ever seen before and
with
details impossible to detect with any other facility. We request 6
more
orbits of Hubble time (1 orbit every 20 days over the next few
months,
until the object enters Hubble's solar exclusion zone in
late-June
2010) to monitor the evolution of this remarkable object and
further
clarify the nature of this event. These observations may usher
in
a new era of searching for and characterizing collisional events
within
the asteroid belt.
ACS/WFC
11995
CCD
Daily Monitor (Part 2)
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 320 orbits (20 weeks) from 1 February 2010 to 20 June
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/UV
11918
WFC3
UVIS Image Quality
The
UVIS imaging performance over the detector will be assessed
periodically
(every 4 months) in two passbands (F275W and F621M) to
check
for image stability. The field around star 58 in the open cluster
NGC188
is the chosen target because it is sufficiently dense to provide
good
sampling over the FOV while providing enough isolated stars to
permit
accurate PSF (point spread function) measurement. It is available
year-round
and used previously for ACS image quality assessment. The
field
is astrometric, and astrometric guide stars will be used, so that
the
plate scale and image orientation may also be determined if
necessary
(as in SMOV proposals 11436 and 11442). Full frame images will
be
obtained at each of 4 POSTARG offset positions designed to improve
sampling
over the detector.
This
proposal is a periodic repeat (once every 4 months) of visits
similar
to those in SMOV proposal 11436 (activity ID WFC3-23). The data
will
be analyzed using the code and techniques described in ISR WFC3
2008-40
(Hartig). Profiles of encircled energy will be monitored and
presented
in an ISR. If an update to the SIAF is needed, (V2, V3)
locations
of stars will be obtained from the Flight Ops Sensors and
Calibrations
group at GSFC, the (V2, V3) of the reference pixel and the
orientation
of the detector will be determined by the WFC3 group, and
the
Telescopes group will update and deliver the SIAF to the PRDB
branch.
The
specific PSF metrics to be examined are encircled energy for
aperture
diameter 0.15, 0.20, 0.25, and 0.35 arcsec, FWHM, and
sharpness.
(See ISR WFC3 2008-40 tables 2 and 3 and preceding text.)
about
20 stars distributed over the detector will be measured in each
exposure
for each filter. The mean, rms, and rms of the mean will be
determined
for each metric. The values determined from each of the 4
exposures
per filter within a visit will be compared to each other to
see
to what extent they are affected by "breathing". Values will be
compared
from visit to visit, starting with the values obtained during
SMOV
after the fine alignment has been performed, to see if the measures
of
the compactness of the PSF indicate degradation over time. The
analysis
will be repeated for stars on the inner part of the detector
and
stars on the outer part of the detector to check for differential
degradation
of the PSF.
As
an example of the analysis, one can examine the sharpness of the
F275W
PSF exposures made during thermal vacuum testing (ISR WFC3
2008-40).
To compare two samples, one can define the PSFs on each CCD
chip
as a sample of 8. The mean, rms, and rms of the mean sharpness are
0.0676,
0.0093, and 0.0035 for one chip, and 0.0701, 0.0085, and 0.0032
for
the other. The difference of the means is 0.0025 and the statistical
error
in that difference is 0.0048, so the difference is not
significant.
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
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).
WFC3/UVIS
11903
UVIS
Photometric Zero Points
This
proposal obtains the photometric zero points in 53 of the 62
UVIS/WFC3
filters: the 18 broad-band filters, 8 medium-band filters, 16
narrow-band
filters, and 11 of the 20 quad filters (those being used in
cycle
17). The observations will be primary obtained by observing the
hot
DA white dwarf standards GD153 and G191-B2B. A redder secondary
standard,
P330E, will be observed in a subset of the filters to provide
color
corrections. Repeat observations in 16 of the most widely used
cycle
17 filters will be obtained once per month for the first three
months,
and then once every second month for the duration of cycle 17,
alternating
and depending on target availability. These observations
will
enable monitoring of the stability of the photometric system.
Photometric
transformation equations will be calculated by comparing the
photometry
of stars in two globular clusters, 47 Tuc and NGC 2419, to
previous
measurements with other telescopes/instruments.
STIS/CC
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/CC
11845
CCD
Dark Monitor Part 2
Monitor
the darks for the STIS CCD.
ACS/WFC/WFC3/IR
11802
WFC3/IR
Observations of Strongly Lensing Clusters
We
propose WFC3/IR observations of the massive lensing clusters Abell
1689
and Abell 1703 to constrain the properties of both cluster and
background
field galaxies. The dataset will also help constrain the
photometric
redshift of A1689-zD1, the bright galaxy candidate at z~7.6.
FGS
11789
An
Astrometric Calibration of Population II Distance Indicators
In
2002, HST produced a highly precise parallax for RR Lyrae. That
measurement
resulted in an absolute magnitude, M(V)= 0.61+/-0.11, a
useful
result, judged by the over ten refereed citations each year
since.
It is, however, unsatisfactory to have the direct,
parallax-based,
distance scale of Population II variables based on a
single
star. We propose, therefore, to obtain the parallaxes of four
additional
RR Lyrae stars and two Population II Cepheids, or W Vir
stars.
The Population II Cepheids lie with the RR Lyrae stars on a
common
K-band Period-Luminosity relation. Using these parallaxes to
inform
that relationship, we anticipate a zero point error of 0.04
magnitude.
This result should greatly strengthen confidence in the
Population
II distance scale and increase our understanding of RR Lyrae
star
and Pop. II Cepheid astrophysics.
STIS/CC/MA
11736
The
Nearest Cold Interstellar Cloud
Optical
observations of interstellar Na I absorption have recently
discovered
that a cold (20 K) diffuse cloud stretching over 10 degrees
across
the constellation Leo is nearby (d < 45 pc) and thus, deep inside
the
Local Bubble of hot, tenuous gas surrounding the Sun out to
distances
of ~100 pc. Assuming thermal pressure equilibrium under these
conditions
leads to an extremely thin, sheetlike geometry for the cold
Leo
cloud. Such a cold cloud could also be the overpressured interface
between
colliding flows of warm gas in the Local Bubble. The keys to
evaluating
the gas pressure and other physical characteristics of the
cold
Leo cloud lie in the ultraviolet with its rich diversity of
interstellar
diagnostic transitions. Due in part to a lack of bright UV
background
sources, there has been no previous UV absorption line study
of
this cloud. We have identified 3 stars exhibiting Na I absorption
from
the cold Leo cloud that are suitable for such a study with STIS
onboard
HST. The main goals of our proposed observations are to: (1)
determine
the cloud's gas pressure through measurements of its C I
fine-structure
excitation, (2) assess the dust contribution to the cloud
heating
by measuring the depletion-sensitive Cr/Zn gas-phase abundance
ratio,
and (3) evaluate the cloud cooling rate and electron density
through
measurements of its C II fine-structure excitation.
WFC3/UVIS
11732
The
Temperature Profiles of Quasar Accretion Disks
We
can now routinely measure the size of quasar accretion disks using
gravitational
microlensing of lensed quasars. At optical wavelengths we
observe
a size and scaling with black hole mass roughly consistent with
thin
disk theory but the sizes are larger than expected from the
observed
optical fluxes. One solution would be to use a flatter
temperature
profile, which we can study by measuring the wavelength
dependence
of the disk size over the largest possible wavelength
baseline.
Thus, to understand the size discrepancy and to probe closer
to
the inner edge of the disk we need to extend our measurements to UV
wavelengths,
and this can only be done with HST. For example, in the UV
we
should see significant changes in the optical/UV size ratio with
black
hole mass. We propose monitoring 5 lenses spanning a broad range
of
black hole masses with well-sampled ground based light curves,
optical
disk size measurements and known GALEX UV fluxes during Cycles
17
and 18 to expand from our current sample of two lenses. We would
obtain
5 observations of each target in each Cycle, similar to our
successful
strategy for the first two targets.
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.
COS/FUV
11687
SNAPing
Coronal Iron
This
is a Snapshot Survey to explore two forbidden lines of highly
ionized
iron in late-type coronal sources. Fe XII 1349 (T~ 2 MK) and Fe
XXI
1354 (T~ 10 MK) -- well known to Solar Physics -- have been detected
in
about a dozen cool stars, mainly with HST/STIS. The UV coronal
forbidden
lines are important because they can be observed with velocity
resolution
of better than 15 km/s, whereas even the state-of-the-art
X-ray
spectrometers on Chandra can manage only 300 km/s in the kilovolt
band
where lines of highly ionized iron more commonly are found. The
kinematic
properties of hot coronal plasmas, which are of great interest
to
theorists and modelers, thus only are accessible in the UV at
present.
The bad news is that the UV coronal forbidden lines are faint,
and
were captured only in very deep observations with STIS. The good
news
is that 3rd-generation Cosmic Origins Spectrograph, slated for
installation
in HST by SM4, in a mere 25 minute exposure with its G130M
mode
can duplicate the sensitivity of a landmark 25-orbit STIS E140M
observation
of AD Leo, easily the deepest such exposure of a late-type
star
so far. Our goal is to build up understanding of the properties of
Fe
XII and Fe XXI in additional objects beyond the current limited
sample:
how the lineshapes depend on activity, whether large scale
velocity
shifts can be detected, and whether the dynamical content of
the
lines can be inverted to map the spatial morphology of the stellar
corona
(as in "Doppler Imaging''). In other words, we want to bring to
bear
in the coronal venue all the powerful tricks of spectroscopic
remote
sensing, well in advance of the time that this will be possible
exploiting
the corona's native X-ray radiation. The 1290-1430 band
captured
by side A of G130M also contains a wide range of key plasma
diagnostics
that form at temperatures from below 10, 000 K (neutral
lines
of CNO), to above 200, 000 K (semi-permitted O V 1371), including
the
important bright multiplets of C II at 1335 and Si IV at 1400;
yielding
a diagnostic gold mine for the subcoronal atmosphere. Because
of
the broad value of the SNAP spectra, beyond the coronal iron project,
we
waive the normal proprietary rights.
WFC3/IR
11666
Chilly
Pairs: A Search for the Latest-type Brown Dwarf Binaries and the
Prototype
Y Dwarf
We
propose to use HST/NICMOS to image a sample of 27 of the nearest (<
20
pc) and lowest luminosity T-type brown dwarfs in order to identify
and
characterize new very low mass binary systems. Only 3 late-type T
dwarf
binaries have been found to date, despite that fact that these
systems
are critical benchmarks for evolutionary and atmospheric models
at
the lowest masses. They are also the most likely systems to harbor Y
dwarf
companions, an as yet unpopulated putative class of very cold (T <
600
K) brown dwarfs. Our proposed program will more than double the
number
of T5-T9 dwarfs imaged at high resolution, with an anticipated
yield
of ~5 new binaries with initial characterization of component
spectral
types. We will be able to probe separations sufficient to
identify
systems suitable for astrometric orbit and dynamical mass
measurements.
We also expect one of our discoveries to contain the first
Y-type
brown dwarf. Our proposed program complements and augments
ongoing
ground-based adaptive optics surveys and provides pathway
science
for JWST.
WFC3/IR/ACS/WFC
11663
Formation
and Evolution of Massive Galaxies in the Richest Environments
at
1.5 < z < 2.0
We
propose to image seven 1.5<z<2 clusters and groups from the IRAC
Shallow
Cluster Survey with WFC3 and ACS in order to study the formation
and
evolution of massive galaxies in the richest environments in the
Universe
in this important redshift range. We will measure the evolution
of
the sizes and morphologies of massive cluster galaxies, as a function
of
redshift, richness, radius and local density. In combination with
allocated
Keck spectroscopy, we will directly measure the dry merger
fraction
in these clusters, as well as the evolution of Brightest
Cluster
Galaxies (BCGs) over this redshift range where clear model
predictions
can be confronted. Finally we will measure both the epoch of
formation
of the stellar populations and the assembly history of that
stellar
mass, the two key parameters in the modern galaxy formation
paradigm.
WFC3/UVIS
11650
Mutual
Orbits, Colors, Masses, and Bulk Densities of 3 Cold Classical
Trans-Neptunian
Binaries
Many
Trans-Neptunian Objects (TNOs) have been found to be binary or
multiple
systems. As in other astrophysical settings, Trans-Neptunian
Binaries
(TNBs) offer uniquely valuable information. Their mutual orbits
allow
the direct determination of their system masses, perhaps the most
fundamental
physical quantity of any astronomical object. Their
frequency
of occurrence and dynamical characteristics provide clues to
formation
conditions and evolution scenarios affecting both the binaries
and
their single neighbors. Combining masses with sizes, bulk densities
can
be measured. Densities constrain bulk composition and internal
structure,
key clues to TNO origins and evolution over time. Several TNB
bulk
densities have been determined, hinting at interesting trends. But
none
of them belongs to the Cold Classical sub-population, the one group
of
TNOs with demonstrably distinct physical characteristics. Two
top-priority
Spitzer programs will soon observe and measure the sizes of
3
Cold Classical TNBs. This proposal seeks to determine the mutual
orbits
and thus masses of these systems, enabling computation of their
densities.
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/UVIS
11643
A
Timeline for Early-Type Galaxy Formation: Mapping the Evolution of
Star
Formation, Globular Clusters, Dust, and Black Holes
While
considerable effort has been devoted to statistical studies of the
origin
of the red sequence of galaxies, there has been relatively little
direct
exploration of galaxies transforming from late to early types.
Such
galaxies are identified by their post-starburst spectra, bulge-
dominated,
tidally-disturbed morphologies, and current lack of gas. We
are
constructing the first detailed timeline of their evolution onto the
red
sequence, pinpointing when star formation ends, nuclear activity
ceases,
globular clusters form, and the bulk of the merging progenitors'
dust
disappears. Here we propose to obtain HST and Chandra imaging of
nine
galaxies, whose wide range of post-starburst ages we have precisely
dated
with a new UV-optical technique and for which we were awarded
Spitzer
time. We will address 1) whether the black hole-bulge mass
relation
arises from nuclear feedback, 2) whether the bimodality of
globular
cluster colors is due to young clusters produced in galaxy
mergers,
and 3) what happens to the dust when late types merge to form
an
early type.
WFC3/UV
11635
Improve
the Measurement of Vesta's Pole Orientation to Support Dawn
Mission
NASA?s
Dawn spacecraft is scheduled to go into orbit around the main
belt
asteroid 4 Vesta in July 2011. Currently the project is using a 3-?
pole
position uncertainty of Vesta of 12? for spacecraft trajectory
design.
We have determined that with an additional set of Hubble
observations
at Vesta?s next opposition in February 2010, that the pole
position
uncertainty can be reduced by a factor of 4. This will reduce
both
cost and risk to the Dawn mission, and is likely to increase the
stay
time at Vesta and will add to the scientific return of the mission.
The
requested observing window in February 2010 is the last and single
best
opportunity that can benefit the Dawn mission, but it is before the
start
of the next HST Cycle.
WFC3/UV/IR
11620
A
Quasar Light Echo in the Local Universe?
The
time history and duty cycle of individual AGN is an important part
of
their evolution and the growth history of massive black holes, but
almost
unconstrained on scales between galaxy-interaction timescales
(hundreds
of Myr) and the scales of years probed by variability
measurements.
We propose a detailed study of an object which seems to be
a
large-scale light echo from a QSO-level episode in a nearby galaxy.
The
Galaxy Zoo morphological survey of SDSS objects has uncovered a
peculiar
emission-line structure whose spectrum matches the narrow-line
region
of AGN, despite lying at least 20 kpc from a galaxy whose
activity
is currently very weak. This is best explained if the nucleus
has
faded dramatically on time scales of several tens of thousands of
years.
We propose a suite of imaging and spectroscopic observations to
probe
its properties, and the time history of this episode of nuclear
activity,
measuring time scales hitherto unavailable.
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/ACS/UVIS/IR
11570
Narrowing
in on the Hubble Constant and Dark Energy
A
measurement of the Hubble constant to a precision of a few percent
would
be a powerful aid to the investigation of the nature of dark
energy
and a potent "end-to end" test of the present cosmological model.
In
Cycle 15 we constructed a new streamlined distance ladder utilizing
high-
quality type Ia supernova data and observations of Cepheids with
HST
in the near-IR to minimize the dominant sources of systematic
uncertainty
in past measurements of the Hubble constant and reduce its
total
uncertainty to a little under 5%. Here we propose to exploit this
new
route to reduce the remaining uncertainty by more than 30%,
translating
into an equal reduction in the uncertainty of the equation
of
state of dark energy. We propose three sets of observations to reach
this
goal: a mosaic of NGC 4258 with WFC3 in F160W to triple its sample
of
long period Cepheids, WFC3/F160W observations of the 6 ideal SN Ia
hosts
to triple their samples of Cepheids, and observations of NGC 5584
the
host of a new SN Ia, SN 2007af, to discover and measure its Cepheids
and
begin expanding the small set of SN Ia luminosity calibrations.
These
observations would provide the bulk of a coordinated program aimed
at
making the measurement of the Hubble constant one of the leading
constraints
on dark energy.
COS/NUV
11561
An
Intensive COS Spectroscopic Study of the Planetary Debris Disks
Around
two Warm White Dwarfs
It
is very likely that the gas giants in our Solar system will survive
the
evolution of the Sun into a white dwarf, and the same is thought to
be
generally true for Jovian planets around solar-like stars if their
initial
orbits are wider than ~3AU. Despite this prediction, no
unambiguous
detection of a planet around a white dwarf has been
announced
so far. However, over the past few years, about a dozen white
dwarfs
have been identified which host metal-rich debris disks that are
thought
to stem from the tidal disruption of asteroids. In most cases
the
debris disks are observed in the form of an infrared flux excess,
and
offer relatively little diagnostic potential for the study of their
structure.
We have discovered three warm (T~20000K) white dwarfs with
metal-rich
debris disks in a gaseous phase which display strong
double-peaked
CaII emission lines in the I-band and weak Fe 5169A
emission.
The line profiles can be modeled in terms of Keplerian disks
with
an extension of ~1Rsun around the white dwarfs. Photospheric MgII
4481A
absorption demonstrates that the white dwarfs are accreting from
the
debris disks. Besides these spectral features, the optical
wavelength
range is devoid of other useful metal transitions. Here, we
propose
an intensive spectroscopic ultraviolet study of these systems,
which
will provide (a) ~1000 photospheric absorption lines of 15
chemical
elements, allowing an accurate abundance study of the material
accreted
from the debris disks, and (b) ~2 dozen additional emission
lines
of Mg, Cr, Ti, and Fe that will provide detailed insight into the
dynamical,
thermal, and density structure of these exo-planetary debris
disks.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
12236
- GSAcq(1,2,1) at 093/21:14:08z failed to RGA control with Search
Radius Limit exceeded on FGS 1.
Observations affected: COS 137 - 141, proposal ID#11687.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS
GSAcq
22
21
FGS
REAcq
25
25
OBAD
with Maneuver 18 18
SIGNIFICANT
EVENTS: (None)