Daily Report #5084

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5084

PERIOD COVERED: 5am April 27 - 5am April 28, 2010 (DOY 117/09:00z-118/09:00z)

OBSERVATIONS SCHEDULED

ACS/WFC/WFC3/UV 11578

The Extremely Metal-Poor BCD Galaxy DDO 68: a Young Galaxy in the
Local Universe ?

A long standing question in astrophysics is the existence of young
galaxies, in which stars are now forming for the first time, in the
nearby (i.e., present-day) universe. Such galaxies would be the local
analogs of primordial galaxies observed at high redshift. The most
promising candidates have long been the most metal-poor systems,
including dwarf irregulars (dIrrs) and blue compact dwarfs (BCDs).
However, in many dIrrs and BCDs studied with HST an old (1 Gyr)
underlying stellar population, as traced by red giant branch (RGB)
stars, has been unambiguously detected. Even in I Zw 18, which is the
most-metal poor prototype of the class and long the most controversial
case, our group has recently succeeded in detecting an RGB.
Nonetheless, there remains the possibility that the star formation
histories of BCDs/dIrrs vary from galaxy to galaxy, and that truly
young galaxies do exist in the local universe. A new test of these
issues has only recently become possible with the identification of
DDO 68 as an extremely metal-poor galaxy with an oxygen abundance
equal to that of I Zw 18 (12+(O/H)=7.21). This galaxy is about a
factor of 2-3 closer than I Zw 18, which yields the opportunity to
avoid the many ambiguities that have plagued studies of I Zw 18. Also,
DDO 68 resides in a void, making it more likely that star formation
has been suppressed for a very long time. We will observe DDO 68 with
ACS/WFC in F606W and F814W, plus F658N (Halpha) to correct the broad
F606W for gas contamination. We will use WFC3 in parallel with the
same filters to study radial population gradients. Deep
color-magnitude diagrams (CMDs) reaching the depth of one magnitude
below the predicted RGB tip will be constructed and interpreted based
on synthetic CMD fitting. These data will determine unambiguously
whether DDO 68 has an underlying old (RGB) stellar population or is
forming stars for the first time. Finding just a single nearby
``young'' galaxy would have profound cosmological implications.

COS/NUV/FUV/WFC3/UVIS/IR 11533

COS-GTO: Accretion Flows and Winds of Pre-Main Sequence Stars

COS will obtain spectra of T Tauri stars to study accretion flows and
wind absorption features in ultraviolet emission lines. Observations
of several T Tauri stars with different inclination angles with
respect to the line of sight will determine the temperature
distributions, flow velocities, and column densities of both inflows
and outflows for these stars.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

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/CCD 11852

STIS CCD Spectroscopic Flats C17

The purpose of this proposal is to obtain pixel-to-pixel lamp flat
fields for the STIS CCD in spectroscopic mode.

STIS/CCD/FGS 11848

CCD Read Noise Monitor

This proposal measures the read noise of all the amplifiers (A, B, C,
D) on the STIS CCD using pairs of bias frames. Full-frame and binned
observations are made in both Gain 1 and Gain 4, with binning factors
of 1x1, 1x2, 2x1, and 2x2. All exposures are internals. Pairs of
visits are scheduled monthly for the first four months and then
bi-monthly after that.

WFC3/ACS/IR 11597

Spectroscopy of IR-Selected Galaxy Clusters at 1 z 1.5

We propose to obtain WFC3 G141 and G102 slitless spectroscopy of
galaxy clusters at 1 z 1.5 that were selected from the IRAC survey
of the Bootes NDWFS field. Our IRAC survey contains the largest sample
of spectroscopically confirmed clusters at z 1. The WFC3 grism data
will measure H-alpha to determine SFR, and fit models to the low
resolution continua to determine stellar population histories for the
brighter cluster members, and redshifts for the red galaxies too faint
for ground-based optical spectroscopy.

WFC3/IR 11936

IR Grism Flux Calibration

This program will determine image displacement, spectral trace and
flux calibration for the IR G102 and G141 grisms as a function of
spatial position within the field of view. The HST flux standard GD71
will be observed in a 9-point pattern in the IR field of view, which
will provide the necessary image displacement, spectral trace, and
throughput measurements.

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/ACS/WFC 11636

First Resolved Imaging of Escaping Lyman Continuum

The emission from star-forming galaxies appears to be responsible for
reionization of the universe at z 6. However, the models that
attempt to describe the detailed impact of high-redshift galaxies on
the surrounding inter-galactic medium (IGM) are strongly dependent
upon several uncertain parameters. Perhaps the most uncertain is the
fraction of HI-ionizing photons produced by young stars that escape
into the IGM. Most attempts to measure this "escape fraction" have
produced null results. Recently, a small subset of z~3 Lyman Break
Galaxies (LBGs) has been found exhibiting large escape fractions. It
remains unclear however, what differentiates them from other LBGs.
Several models attempt to explain how such a large fraction of
ionizing continuum can escape through the HI and dust in the ISM (eg.
"chimneys" created by SNe winds, globular cluster formation, etc.),
each producing unique signatures which can be observed with resolved
imaging of the escaping Lyman continuum. To date, there are only six
LBGs with individual detections of escaping Lyman continuum at any
redshift. We propose a single deep, high resolution WFC3/UVIS image of
the ionizing continuum (F336W) and the rest-frame UV/optical
(F606W/F814W/F160W) of five of these six LBGs with large escape
fractions. These LBGs have a high surface density and large escape
fractions, and lie at the optimal redshift for Lyman continuum imaging
with UVIS filters, making our sample especially suitable for
follow-up. With these data we will discern the mechanisms responsible
for producing large escape fractions, and therefore gain insight into
the process of reionization.

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 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/UVI 11911

UVIS L-Flats and Geometric Distortion

Multiple pointing observations of the globular cluster Omega Centauri
(NGC 5139) will be used to measure the filter-dependent low frequency
flat field (L-flat) corrections and stability for a key set of 10
broadband filters used by GO programs. The selected filters are F225W,
F275W, F336W, F390W, F438W, F555W, F606W, F775W, F814W and F850LP. By
measuring relative changes in brightness of a star over different
portions of the detector, we will determine local variations in the
UVIS detector response. The broad wavelength range covered by these
observations will allow us to derive the L-flat correction for the
remaining wide, medium and narrow-band UVIS filters. The same data
will also be used to determin and correct the geometric distotrion
that affects UVIS data. The broad wavelength range covered by these
observations will allow us to measure the geometric distortion
dependence with wavelength and filters and to provide the most
appropriate correction over the entire wavelength range provided by
UVIS.

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.


FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

12255 - Following successful GSAcq(2,3,3), a Loss of Lock occurred
while guiding with FGS-2, and FGS-3 at 188/04:27:02z. Subsequent
REAcqs(2,3,3) were successful.

Observations possibly affected. WFC3 47 Proposal ID#11911, ACS #85,
Proposal ID#11995.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSAcq 06 06
FGS REAcq 10 10
OBAD with Maneuver 03 03
LOSS of LOCK 118/04:29:57z

SIGNIFICANT EVENTS: (None)