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Daily Report #5040



 
 
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Old February 25th 10, 06:14 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5040

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5040

PERIOD COVERED: 5am February 24 - 5am February 25, 2010 (DOY 055/10:00z-056/10:00z)

OBSERVATIONS SCHEDULED

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.

COS/NUV/FUV 11718

The Stellar Halos of Dwarf Galaxies

The metal-poor stellar halo is the oldest extended structure in the
Galaxy. Such halos are thought to form through hierarchical merging,
and contain stars pulled from accreted subhalos. The diffuse stellar
halo therefore stores information about the prop reties of the
accreted galaxies (i.e., their orbits, stellar masses, and
metallicities). It is therefore unsurprising that stellar halos have
become a popular probe of the early epoch of galaxy formation.

Almost all current work on stellar halos has focused on massive
galaxies, however. We propose to extend the work on stellar halos to
much lower mass scales, by studying the halos of faint dwarf galaxies.
By taking halo studies into the dwarf galaxy regime, we can probe
exceptionally small mass scales for the accreted halos. At these mass
scales the effects of reionization and supernova feedback have the
largest impact on the galaxy population. Stellar halos of dwarf
galaxies are therefore a sensitive probe of the key processes needed
to resolve the lack of substructure observed at low masses.

We are requesting two far-field ACS pointings for the three closest
isolated nearby dwarf irregular galaxies whose inner halos have
already been mapped with the ACS Nearby Galaxy Survey Treasury. These
outer fields will allow us to trace the halo out to roughly half the
virial radius, further than any previous study. We will use the
resulting distribution of halo stars (1) to unambiguously measure the
structure of the stellar halo, with minimal contamination from the
main galaxy; (2) to constrain the flattening of the stellar halo; (3)
to measure the metallicity of halo stars as a function of radius; (4)
to correlate any changes in halo profile with changes in metallicity.
The resulting data will constrain models of halo accretion and the
epoch of reionization.

STIS/CCD 11844

CCD Dark Monitor Part 1

The purpose of this proposal is to monitor the darks for the STIS CCD.

STIS/CCD 11846

CCD Bias Monitor-Part 1

The purpose of this proposal is to 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/MA1/MA2 11857

STIS Cycle 17 MAMA Dark Monitor

This proposal monitors the behavior of the dark current in each of the
MAMA detectors.

The basic monitor takes two 1380s ACCUM darks each week with each
detector. However, starting Oct 5, pairs are only included for weeks
that the LRP has external MAMA observations planned. The weekly pairs
of exposures for each detector are linked so that they are taken at
opposite ends of the same SAA free interval. This pairing of exposures
will make it easier to separate long and short term temporal
variability from temperature dependent changes.

For both detectors, additional blocks of exposures are taken once
every six months. These are groups of five 1314s FUV-MAMA Time-Tag
darks or five 3x315s NUV ACCUM darks distributed over a single
SAA-free interval. This will give more information on the brightness
of the FUV MAMA dark current as a function of the amount of time that
the HV has been on, and for the NUV MAMA will give a better measure of
the short term temperature dependence.

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.

WFC3/IR 11189

Probing the Early Universe with GRBs

Cosmology is beginning to constrain the nature of the earliest stars
and galaxies to form in the Universe, but direct observation of
galaxies at z6 remains highly challenging due to their scarcity,
intrinsically small size, and high luminosity distance. GRB
afterglows, thanks to their extreme luminosities, offer the
possibility of circumventing these normal constraints by providing
redshifts and spectral information which couldn't be obtained through
direct observation of the host galaxies themselves. In addition, the
association of GRBs with massive stars means that they are an
indicator of star formation, and that their hosts are likely
responsible for a large proportion of the ionizing radiation during
that era. Our collaboration is conducting a campaign to rapidly
identify and study candidate very high redshift bursts, bringing to
bear a network of 2, 4 and 8m telescopes with near-IR instrumentation.
Swift has proven capable of detecting faint, distant GRBs, and
reporting accurate positions for many bursts in near real-time. Here
we propose to continue our HST program of targeting GRBs at z~6 and
above. HST is crucial to this endeavor, allowing us (a) to
characterize the basic properties, such as luminosity and color, and
in some cases morphologies, of the hosts, which is essential to
understanding these primordial galaxies and their relationship to
other galaxy populations; and (b) to monitor the late time afterglows
and hence compare them to lower-z bursts and test the use of GRBs as
standard candles.

WFC3/IR 11719

A Calibration Database for Stellar Models of Asymptotic Giant Branch
Stars

Studies of galaxy formation and evolution rely increasingly on the
interpretation and modeling of near-infrared observations. At these
wavelengths, the brightest stars are intermediate mass asymptotic
giant branch (AGB) stars. These stars can contribute nearly 50% of the
integrated luminosity at near infrared and even optical wavelengths,
particularly for the younger stellar populations characteristic of
high-redshift galaxies (z1). AGB stars are also significant sources
of dust and heavy elements. Accurate modeling of AGB stars is
therefore of the utmost importance.

The primary limitation facing current models is the lack of useful
calibration data. Current models are tuned to match the properties of
the AGB population in the Magellanic Clouds, and thus have only been
calibrated in a very narrow range of sub-solar metallicities.
Preliminary observations already suggest that the models are
overestimating AGB lifetimes by factors of 2-3 at lower metallicities.
At higher (solar) metallicities, there are no appropriate observations
for calibrating the models.

We propose a WFC3/IR SNAP survey of nearby galaxies to create a large
database of AGB populations spanning the full range of metallicities
and star formation histories. Because of their intrinsically red
colors and dusty circumstellar envelopes, tracking the numbers and
bolometric fluxes of AGB stars requires the NIR observations we
propose here. The resulting observations of nearby galaxies with deep
ACS imaging offer the opportunity to obtain large (100-1000's)
complete samples of AGB stars at a single distance, in systems with
well-constrained star formation histories and metallicities.

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 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.

WFC3/UVIS 11594

A WFC3 Grism Survey for Lyman Limit Absorption at z=2

We propose to conduct a spectroscopic survey of Lyman limit absorbers
at redshifts 1.8 z 2.5, using WFC3 and the G280 grism. This
proposal intends to complete an approved Cycle 15 SNAP program
(10878), which was cut short due to the ACS failure. We have selected
64 quasars at 2.3 z 2.6 from the Sloan Digital Sky Survey
Spectroscopic Quasar Sample, for which no BAL signature is found at
the QSO redshift and no strong metal absorption lines are present at z
2.3 along the lines of sight. The survey has three main

observational goals. First, we will determine the redshift frequency
dn/dz of the LLS over the column density range 16.0 log(NHI) 20.3
cm^-2. Second, we will measure the column density frequency
distribution f(N) for the partial Lyman limit systems (PLLS) over the
column density range 16.0 log(NHI) 17.5 cm^-2. Third, we will
identify those sightlines which could provide a measurement of the
primordial D/H ratio. By carrying out this survey, we can also help
place meaningful constraints on two key quantities of cosmological
relevance. First, we will estimate the amount of metals in the LLS
using the f(N), and ground based observations of metal line
transitions. Second, by determining f(N) of the PLLS, we can constrain
the amplitude of the ionizing UV background at z~2 to a greater
precision. This survey is ideal for a snapshot observing program,
because the on-object integration times are all well below 30 minutes,
and follow-up observations from the ground require minimal telescope
time due to the QSO sample being bright.

WFC3/UVIS 11595

Turning Out the Light: A WFC3 Program to Image z2 Damped Lyman Alpha
Systems

We propose to directly image the star-forming regions of z2 damped
Lya systems (DLAs) using the WFC3/UVIS camera on the Hubble Space
Telescope. In contrast to all previous attempts to detect the galaxies
giving rise to high redshift DLAs, we will use a novel technique that
completely removes the glare of the background quasar. Specifically,
we will target quasar sightlines with multiple DLAs and use the higher
redshift DLA as a ``blocking filter'' (via Lyman limit absorption) to
eliminate all FUV emission from the quasar. This will allow us to
carry out a deep search for FUV emission from the lower redshift DLA,
shortward of the Lyman limit of the higher redshift absorber. The
unique filter set and high spatial resolution afforded by WFC3/UVIS
will then enable us to directly image the lower redshift DLA and thus
estimate its size, star- formation rate and impact parameter from the
QSO sightline. We propose to observe a sample of 20 sightlines,
selected primarily from the SDSS database, requiring a total of 40 HST
orbits. The observations will allow us to determine the first FUV
luminosity function of high redshift DLA galaxies and to correlate the
DLA galaxy properties with the ISM characteristics inferred from
standard absorption-line analysis to significantly improve our
understanding of the general DLA population.

WFC3/UVIS 11786

HST Observations of Astrophysically Important Visual Binaries

This is a continuation of a project begun in Cycle 7 and continued up
through Cycle 14. The program consists of annual FGS or WFPC2
observations of three visual binary stars that will yield fundamental
astrophysical results, once their orbits and masses are determined. In
Cycle 17 we are changing WFPC2 to WFC3.

Our targets are the following: (1) Procyon (P = 40.9 yr), for which
our first WFPC2 images yielded an extremely accurate angular
separation of the bright F star and its much fainter white- dwarf
companion. Combined with ground-based astrometry of the bright star,
our observation significantly revised downward the derived masses, and
brought Procyon A into much better agreement with theoretical
evolutionary masses for the first time. With the continued monitoring
proposed here, we will obtain masses to an accuracy of better than 1%,
providing a testbed for theories of both Sun-like stars and white
dwarfs. (2) G 107-70, a close double white dwarf (P = 18.5 yr) that
promises to add two accurate masses to the tiny handful of white-dwarf
masses that are directly known from dynamical measurements. (3) Mu Cas
(P = 20.8 yr), a famous nearby metal-deficient G dwarf for which
accurate masses will lead to the stars' helium contents, with
cosmological implications. For all three stars, we will also be
setting increasingly stringent limits on the presence of
planetary-mass bodies in the systems.

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 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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 7 7
FGS REAcq 9 9
OBAD with Maneuver 4 4

SIGNIFICANT EVENTS: (None)


 




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