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

z>6 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 (z>1). 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 z>2 Damped Lyman Alpha

Systems

We propose to directly image the star-forming regions of z>2 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)