Daily # 4265

THE NEXT REPORT WILL BE PUBLISHED ON DECEMBER 26th 2006


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4265

PERIOD COVERED: UT December 21, 2006 (DOY 355)

OBSERVATIONS SCHEDULED

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the
neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy,
they could only be studied from the ground at redshifts z1.65.
However, HST has now permitted us to discover 41 DLAs at z1.65 in our
previous surveys. Followup studies of these systems are providing a
wealth of information about the evolution of the neutral gas phase
component of the Universe. But one problem is that these 41
low-redshift systems are spread over a wide range of redshifts
spanning nearly 70% of the age of the Universe. Consequently, past
surveys for low-redshift DLAs have not been able to offer very good
precision in any small redshift regime. Here we propose an ACS-HRC-
PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7]
which we estimate will permit us to discover another 41 DLAs. This
will not only allow us to double the number of low-redshift DLAs, but
it will also provide a relatively high-precision regime in the
low-redshift Universe that can be used to anchor evolutionary studies.
Fortunately DLAs have high absorption equivalent width, so
ACS-HRC-PR200L has high-enough resoultion to perform this proposed
MgII-selected DLA survey.

ACS/HRC 10800

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the
early dynamical evolution of the outer Solar System. We propose to
continue a Snapshot program using the ACS/HRC that has a demonstrated
discovery potential an order of magnitude higher than the HST
observations that have already discovered the majority of known
transneptunian binaries. With this continuation we seek to reach the
original goals of this project: to accumulate a sufficiently large
sample in each of the distinct populations collected in the Kuiper
Belt to be able to measure, with statistical significance, how the
fraction of binaries varies as a function of their particular
dynamical paths into the Kuiper Belt. Today's Kuiper Belt bears the
imprints of the final stages of giant-planet building and migration;
binaries may offer some of the best preserved evidence of that
long-ago era.

ACS/HRC/WFPC2/NIC3 10842

A Cepheid Distance to the Coma Cluster

We propose to use the Advanced Camera for Surveys to search for
Cepheid variables in two spiral galaxies in the core of the Coma
cluster. A direct application of the canonical primary distance
indicator at 100 Mpc will measure the far-field Hubble constant free
of many of the systematic uncertainties which beset current
determinations relying on secondary indicators. Establishing the
far-field H_o with Cepheids will provide one of the strongest links in
the extragalactic distance scale and will directly calibrate the
fiducial fundamental plane of elliptical galaxies in Coma. With
ACS/HRC, S/N=5 to 10 or better can be reached for Cepheids with
periods of 40d to 70d at mean light in 5 orbits with the F606W filter
if H_o=72 km/s/Mpc. Efficient detection and phasing can be done with
twelve epochs optimally spaced for periods of 40-70d.

ACS/WFC 10809

The nature of "dry" mergers in the nearby Universe

Recent studies have shown that "dry" mergers of red, bulge-dominated
galaxies at low redshift play an important role in shaping today's
most massive ellipticals. These mergers have been identified in
extremely deep ground-based images of red sequence galaxies at z ~
0.1. The ground-based images reach surface brightness limits of AB ~
29, but lack the resolution to study the morphologies of the galaxies
inside the effective radius. Here we propose to obtain ACS images of a
representative sample of 40 of these red sequence galaxies: 15 ongoing
dry mergers, 15 remnants, and 10 undisturbed objects. We will measure
the isophote shapes and ellipticities of the galaxies, their dust
content, morphological fine structure {shells and ripples}, AGN
content, and their location on the Fundamental Plane. By comparing
galaxies in different stages of the merging process we can constrain
the amount of gas associated with these red mergers, the effect of
active nuclei, and track structural changes. As two galaxies can be
observed in a single orbit 20 orbits are requested to observe the 40
galaxies.

ACS/WFC 10831

A new wide-separation Einstein Cross at z=2.7

We propose ACS F555W and F814W imaging observations of a new
wide-separation Einstein Cross selected from SDSS spectroscopy through
a bright anomalous emission line and confirmed recently with Keck
imaging and spectroscopy. The source galaxy is a moderately luminous
{L~0.2L*} Lyman-alpha emitter at z=2.699, which is magnified and
extended by more than a factor of twenty, making it one of the most
accessible high-redshift bright Ly-a emitters on the sky. Its apparent
flux is only 1.2 magnitudes fainter than MS1612-cB58, making this an
ideal system for detailed study of the metallicity and initial mass
function of a high-redshift star forming galaxy. The Einstein Radius
is ~1.8arcsec, one of the widest known, making future spectroscopic
ground-based followup optimal. This angle subtends ~5 kpc at the lens
galaxy at z=0.331. The high resolution, high signal to noise imaging
we propose to obtain will allow us to build accurate lensing models,
including source reconstructions; combined with existing and planned
Keck spectroscopy, will make possible a map of the host dark matter
halo density profile to greater than one effective light radius; and
will reveal lower surface brightness features associated with the
bright star-forming knot lensed into the Cross. Finally, it will be an
exquisite Hubble Heritage galaxy, which will be indispensable for many
other applications. We are requesting a very modest proprietary
period, in order to provide high-level reductions and ancillary data
publically available simultaneously.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in
parallel in all three NICMOS Cameras. The POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword 'USEAFTER=date/time' will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting
in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at
redshifts exceeding 1 are now the leading obstacles to determining the
nature of dark energy. We propose a single, integrated set of
observations for Cycle 15 that will provide a 40% improvement in
constraints on dark energy. This program will observe known Cepheids
in six reliable hosts of Type Ia supernovae with NICMOS, reducing the
uncertainty in H_0 by a factor of two because of the smaller
dispersion along the instability strip, the diminished extinction, and
the weaker metallicity dependence in the infrared. In parallel with
ACS, at the same time the NICMOS observations are underway, we will
discover and follow a sample of Type Ia supernovae at z 1. Together,
these measurements, along with prior constraints from WMAP, will
provide a great improvement in HST's ability to distinguish between a
static, cosmological constant and dynamical dark energy. The Hubble
Space Telescope is the only instrument in the world that can make
these IR measurements of Cepheids beyond the Local Group, and it is
the only telescope in the world that can be used to find and follow
supernovae at z 1. Our program exploits both of these unique
capabilities of HST to learn more about one of the greatest mysteries
in science.

WFPC2 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and
highly non-uniform archive, making comprehensive comparative studies
among galaxies essentially impossible. We propose to secure HST's
lasting impact on the study of nearby galaxies by undertaking a
systematic, complete, and carefully crafted imaging survey of ALL
galaxies in the Local Universe outside the Local Group. The resulting
images will allow unprecedented measurements of: {1} the star
formation history {SFH} of a 100 Mpc^3 volume of the Universe with a
time resolution of Delta[log{t}]=0.25; {2} correlations between
spatially resolved SFHs and environment; {3} the structure and
properties of thick disks and stellar halos; and {4} the color
distributions, sizes, and specific frequencies of globular and disk
clusters as a function of galaxy mass and environment. To reach these
goals, we will use a combination of wide-field tiling and pointed deep
imaging to obtain uniform data on all 72 galaxies within a
volume-limited sample extending to ~3.5 Mpc, with an extension to the
M81 group. For each galaxy, the wide-field imaging will cover out to
~1.5 times the optical radius and will reach photometric depths of at
least 2 magnitudes below the tip of the red giant branch throughout
the limits of the survey volume. One additional deep pointing per
galaxy will reach SNR~10 for red clump stars, sufficient to recover
the ancient SFH from the color-magnitude diagram. This proposal will
produce photometric information for ~100 million stars {comparable to
the number in the SDSS survey} and uniform multi-color images of half
a square degree of sky. The resulting archive will establish the
fundamental optical database for nearby galaxies, in preparation for
the shift of high-resolution imaging to the near-infrared.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10567 - REacq(2,1,1) failed to RGA control

The REacq(2,1,1) scheduled at 355/17:55:05 failed to RGA control. At
AOS 17:59:00 flags were set indicating the REacq failed due to
receiving stop flags QF2STOPF and QSTOP. OBAD1 had errors of V1=
-25.12, V2=-1180.99, V3=-10.73 and RSS=1181.31. OBAD2 showed errors of
V1=-1.06, V2=3.48, V3=-2.47 and RSS= 4.40. The Map at 18:02 showed
erros of V1=-1.88, V2=1.23, V3=-2.42 and RSS=3.30.

10568 - REAcq (2,1,1) failed to RGA Hold (Gyro Control)

At 355/19:42:15 REAcq (2,1,1) scheduled from 355/19:31:05-19:38:16 had
failed to RGA Hold (Gyro Control). Flag for QF2STOPF was set. OBAD #1
RSS: 482.12 OBAD #2 RSS: 5.49 OBAD MAP: Not scheduled

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 08
FGS REacq 07 05
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS: (None)