Daily Report #4959

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #4959

PERIOD COVERED: 5am October 26 - 5am October 27, 2009 (DOY 299/09:00z-300/09:00z)

OBSERVATIONS SCHEDULED

ACS/WFC3 11879

CCD Daily Monitor (Part 1)

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 352 orbits (22 weeks) from 31 August
2009 to 31 January 2010.

COS/FUV 11895

FUV Detector Dark Monitor

The purpose of this proposal is to monitor the FUV detector dark rate
by taking long science exposures without illuminating the detector.
The detector dark rate and spatial distribution of counts will be
compared to pre-launch and SMOV data in order to verify the nominal
operation of the detector. Variations of count rate as a function of
orbital position will be analyzed to find dependence of dark rate on
proximity to the SAA. Dependence of dark rate as function of time will
also be tracked.

FGS 11704

The Ages of Globular Clusters and the Population II Distance Scale

Globular clusters are the oldest objects in the universe whose age can
be accurately determined. The dominant error in globular cluster age
determinations is the uncertain Population II distance scale. We
propose to use FGS 1R to obtain parallaxes with an accuracy of 0.2
milliarcsecond for 9 main sequence stars with [Fe/H] -1.5. This will
determine the absolute magnitude of these stars with accuracies of
0.04 to 0.06mag. This data will be used to determine the distance to
24 metal-poor globular clusters using main sequence fitting. These
distances (with errors of 0.05 mag) will be used to determine the ages
of globular clusters using the luminosity of the subgiant branch as an
age indicator. This will yield absolute ages with an accuracy of 5%,
about a factor of two improvement over current estimates. Coupled with
existing parallaxes for more metal-rich stars, we will be able to
accurately determine the age for globular clusters over a wide range
of metallicities in order to study the early formation history of the
Milky Way and provide an independent estimate of the age of the
universe.

The Hipparcos database contains only 1 star with [Fe/H] -1.4 and an
absolute magnitude error less than 0.18 mag which is suitable for use
in main sequence fitting. Previous attempts at main sequence fitting
to metal-poor globular clusters have had to rely on theoretical
calibrations of the color of the main sequence. Our HST parallax
program will remove this source of possible systematic error and yield
distances to metal-poor globular clusters which are significantly more
accurate than possible with the current parallax data. The HST
parallax data will have errors which are 10 times smaller than the
current parallax data. Using the HST parallaxes, we will obtain main
sequence fitting distances to 11 globular clusters which contain over
500 RR Lyrae stars. This will allow us to calibrate the absolute
magnitude of RR Lyrae stars, a commonly used Population II distance
indicator.

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.

FGS 11871

Long Term Stability of FGS1R in Position Mode

This proposal resumes the Long Term Monitoring of FGS1R in Position
Mode using stars in M35 that are a subset of the FGS "OFAD catalog"
using both the "fall" and "spring" seasons (the spring orient was not
available under two gyro mode). The data acquired by this proposal are
used to update the FGS1R "rhoA & kA" parameters that are associated
with the OFAD solution that is applicable at the observation's epoch.
These values are critical to support sub-milli arcsecond astrometry
with FGS1R.

This particular proposal also include a FGS3 visit to M35 for post SM4
verification of its calibration status.

NIC2/WFC3/IR 11548

Infrared Imaging of Protostars in the Orion A Cloud: The Role of
Environment in Star Formation

We propose NICMOS and WFC3/IR observations of a sample of 252
protostars identified in the Orion A cloud with the Spitzer Space
Telescope. These observations will image the scattered light escaping
the protostellar envelopes, providing information on the shapes of
outflow cavities, the inclinations of the protostars, and the overall
morphologies of the envelopes. In addition, we ask for Spitzer time to
obtain 55-95 micron spectra of 75 of the protostars. Combining these
new data with existing 3.6 to 70 micron photometry and forthcoming
5-40 micron spectra measured with the Spitzer Space Telescope, we will
determine the physical properties of the protostars such as envelope
density, luminosity, infall rate, and outflow cavity opening angle. By
examining how these properties vary with stellar density (i.e.
clusters vs. groups vs. isolation) and the properties of the
surrounding molecular cloud; we can directly measure how the
surrounding environment influences protostellar evolution, and
consequently, the formation of stars and planetary systems.
Ultimately, this data will guide the development of a theory of
protostellar evolution.

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/CCD/MA1 11525

COS-GTO: STIS High Resolution Observations of the Local ISM

We shall use bright early-type B stars located within 150pc of the Sun
to probe the absorption properties of the interstellar gas associated
with the local cavity. By utilizing the high sensitivity and high
spectral resolution of the HST-STIS spectrograph we shall be able to
place new detection limits on absorption occurring in any highly
ionized gas associated with the lines of NV, SiIV and CIV that may be
present along these sight-lines within the local cavity. These data
will be used to test current theoretical models that generally predict
far higher absorption column densities than have been previously
found. Also, the high spectral resolution will enable far stricter
limits to be placed on the thermal widths of such highly ionized
absorption lines, which previous observations towards the Loop I
region have suggested anomalously narrow profiles consistent with
their formation by either photo ionization or highly non-equilibrium
processes.

WFC3/ACS/UVIS 11360

Star Formation in Nearby Galaxies

Star formation is a fundamental astrophysical process; it controls
phenomena ranging from the evolution of galaxies and nucleosynthesis
to the origins of planetary systems and abodes for life. The WFC3,
optimized at both UV and IR wavelengths and equipped with an extensive
array of narrow-band filters, brings unique capabilities to this area
of study. The WFC3 Scientific Oversight Committee (SOC) proposes an
integrated program on star formation in the nearby universe which will
fully exploit these new abilities. Our targets range from the
well-resolved R136 in 30 Dor in the LMC (the nearest super star
cluster) and M82 (the nearest starbursting galaxy) to about half a
dozen other nearby galaxies that sample a wide range of star-formation
rates and environments. Our program consists of broad band
multiwavelength imaging over the entire range from the UV to the
near-IR, aimed at studying the ages and metallicities of stellar
populations, revealing young stars that are still hidden by dust at
optical wavelengths, and showing the integrated properties of star
clusters. Narrow-band imaging of the same environments will allow us
to measure star-formation rates, gas pressure, chemical abundances,
extinction, and shock morphologies. The primary scientific issues to
be addressed a (1) What triggers star formation? (2) How do the
properties of star-forming regions vary among different types of
galaxies and environments of different gas densities and compositions?
(3) How do these different environments affect the history of star
formation? (4) Is the stellar initial mass function universal or
determined by local conditions?

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 11730

Continued Proper Motions of the Magellanic Clouds: Orbits, Internal
Kinematics, and Distance

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields
in the Magellanic Clouds centered on background quasars. We used these
data to determine the proper motions of the LMC and SMC to better than
5% and 15% respectively. The results had a number of unexpected
implications for the Milky Way-LMC-SMC system and received
considerable attention in the literature and in the press. The implied
three-dimensional velocities are larger than previously believed and
close to the escape velocity in a standard 10^12 solar mass Milky Way
dark halo. Our orbit calculations suggest the Clouds may not be bound
to the Milky Way or may just be on their first passage, both of which
are unexpected in view of traditional interpretations of the
Magellanic Stream. Alternatively, the Milky Way dark halo may be a
factor two more massive than previously believed, which would be
surprising in view of other observational constraints. Also, the
relative velocity between the LMC and SMC was larger than expected,
leaving open the possibility that the Clouds may not be bound to each
other. To further verify and refine our results we requested an
additional epoch data in Cycle 16 which is being executed with
WFPC2/PC due to the failure of ACS. A detailed analysis of one LMC
field shows that the field proper motion using all three epochs of
data is consistent within 1-sigma with the two-epoch data, thus
verifying that there are no major systematic effects in our previous
measurements. The random errors, however, are only smaller by a factor
of 1.4 because of the relatively large errors in the WFPC2 data. A
prediction for a fourth epoch with measurement errors similar to
epochs 1 and 2 shows that the uncertainties will improve by a factor
of 3. This will allow us to better address whether the Clouds are
indeed bound to each other and to the Milky Way. It will also allow us
to constrain the internal motions of various populations within the
Clouds, and to determine a distance to the LMC using rotational
parallax. Continuation of this highly successful program is therefore
likely to provide important additional insights. Execution in SNAPshot
mode guarantees maximally efficient use of HST resources.

WFC3/UVIS 11565

A Search for Astrometric Companions to Very Low-Mass, Population II
Stars

We propose to carry out a Snapshot search for astrometric companions
in a subsample of very low-mass, halo subdwarfs identified within 120
parsecs of the Sun. These ultra-cool M subdwarfs are local
representatives of the lowest-mass H burning objects from the Galactic
Population II. The expected 3-4 astrometric doubles that will be
discovered will be invaluable in that they will be the first systems
from which gravitational masses of metal-poor stars at the bottom of
the main sequence can be directly measured.

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).

WFPC2/NIC3/ACS/SBC 11144

Building on the Significant NICMOS Investment in GOODS: A Bright,
Wide-Area Search for z=7 Galaxies

One of the most exciting frontiers in observational cosmology has been
to trace the buildup and evolution of galaxies from very early times.
While hierarchical theory teaches us that the star formation rate in
galaxies likely starts out small and builds up gradually, only
recently has it been possible to see evidence for this observationally
through the evolution of the LF from z~6 to z~3. Establishing that
this build up occurs from even earlier times {z~7-8} has been
difficult, however, due to the small size of current high-redshift
z~7-8 samples -- now numbering in the range of ~4-10 sources.
Expanding the size of these samples is absolutely essential, if we are
to push current studies of galaxy buildup back to even earlier times.
Fortunately, we should soon be able to do so, thanks to ~50 arcmin**2
of deep {26.9 AB mag at 5 sigma} NICMOS 1.6 micron data that will be
available over the two ACS GOODS fields as a result of one recent
180-orbit ACS backup program and a smaller program. These data will
nearly triple the deep near-IR imaging currently available and
represent a significant resource for finding and characterizing the
brightest high-redshift sources -- since high-redshift candidates can
be easily identified in these data from their red z-H colours.
Unfortunately, the red z-H colours of these candidates are not
sufficient to determine that these sources are at z=7, and it is
important also to have deep photometry at 1.1 microns. To obtain this
crucial information, we propose to follow up each of these z-H
dropouts with NICMOS at 1.1 microns to determine which are at high
redshift and thus significantly expand our sample of luminous, z=7
galaxies. Since preliminary studies indicate that these candidates
occur in only 30% of the NIC3 fields, our follow-up strategy is ~3
times as efficient as without this preselection and 9 times as
efficient as a search in a field with no pre- existing data. In total,
we expect to identify ~8 luminous z-dropouts and possibly ~2 z~10 J-
dropouts as a result of this program, more than tripling the number
currently known. The increased sample sizes are important if we are to
solidify current conclusions about galaxy buildup and the evolution of
the LF from z~8. In addition to the high redshift science, these deep
1.1 micron data would have significant value for many diverse
endeavors, including {1} improving our constraints on the stellar mass
density at z~7-10 and {2} doubling the number of galaxies at z~6 for
which we can estimate dust obscuration.

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 11 11
FGS REAcq 05 05
OBAD with Maneuver 07 07

SIGNIFICANT EVENTS: (None)