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Daily Report #5067



 
 
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Old April 5th 10, 03:27 PM posted to sci.astro.hubble
Cooper, Joe
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Posts: 568
Default Daily Report #5067

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 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.

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 1.5z2 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)

 




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