Daily Report #4260

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4260

PERIOD COVERED: UT December 14, 2006 (DOY 348)

OBSERVATIONS SCHEDULED

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 10795

The Largest Galaxies in the Local Universe: New Light on Disk Galaxy
Formation?

In the standard scenario of disk galaxy formation in a hierarchical
Universe, large disks form late via the accretion of either hot or
cold gas. Direct observational evidence for such late accretion-
driven disk formation has not been forthcoming. In this proposal, we
describe the discovery of a rare new type of galaxy that may be
examples of massive disks in the process of assembly. We have
identified a sample of three such galaxies selected from the SDSS DR4.
They are extremely large {diameters over 100 kpc} and highly luminous
systems with amorphous structures {no obvious spiral arms or bulges}.
They are larger than the largest normal spirals in the survey, and
have significantly bluer colors, lower metallicities, lower dust
extinctions, higher UV luminosities and higher total star formation
rates than the most massive ordinary spirals. We request HST images in
the rest-frame near-UV and red to provide detailed maps of the
underlying structure of these galaxies as well as the distribution of
the young stars. The interstellar medium of these galaxies is
evidently quite different from that of normal large spirals and
starburst galaxies and they may be experiencing a different mode of
star formation. We believe they are worthy of further investigation
with the high-resolution imaging capabilities of HST.

ACS/WFC 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS}
Survey for new strong gravitational lenses, we propose one orbit of
ACS-WFC F814W imaging for each of 50 high- probability strong
galaxy-galaxy lens candidates. These observations will confirm new
lens systems and permit immediate and accurate photometry, shape
measurement, and mass modeling of the lens galaxies. The lenses
delivered by the SLACS Survey all show extended source structure,
furnishing more constraints on the projected lens potential than
lensed-quasar image positions. In addition, SLACS lenses have lens
galaxies that are much brighter than their lensed sources,
facilitating detailed photometric and dynamical observation of the
former. When confirmed lenses from this proposal are combined with
lenses discovered by SLACS in Cycles 13 and 14, we expect the final
SLACS lens sample to number 80--100: an approximate doubling of the
number of known galaxy-scale strong gravitational lenses and an
order-of-magnitude increase in the number of optical Einstein rings.
By virtue of its homogeneous selection and sheer size, the SLACS
sample will allow an unprecedented exploration of the mass structure
of the early-type galaxy population as a function of all other
observable quantities. This new sample will be a valuable resource to
the astronomical community by enabling qualitatively new strong
lensing science, and as such we will waive all but a short {3-month}
proprietary period on the observations.

ACS/WFC 10905

The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region

With accurate distances, the nearest groups of galaxies can be
resolved in 3 dimensions and the radial component of the motions of
galaxies due to local density perturbations can be distinquished from
cosmological expansion components. Currently, with the ACS, galaxy
distances within 8 Mpc can be measured effectively and efficiently by
detecting the tip of the red giant branch {TRGB}. Of four principal
groups at high galactic latitude in this domain, the Canes Venatici I
Group {a} is the least studied, {b} is the most populated, though
overwhelmingly by dwarf galaxies, and {c} is likely the least
dynamically evolved. It is speculated that galaxies in low mass groups
may fail to retain baryons as effectively as those in high mass
groups, resulting in significantly higher mass-to-light ratios. The
CVn I Group is suspected to lie in the mass regime where the
speculated astrophysical processes that affect baryon retention are
becoming important.

NIC1 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the
thick disks and halos of seven nearby, massive, edge-on galaxies using
ACS, NICMOS, and WFPC2 in parallel. These observations will provide
accurate star counts and color-magnitude diagrams 1.5 magnitudes below
the tip of the Red Giant Branch sampled along the two principal axes
and one intermediate axis of each galaxy. We will measure the
metallicity distribution functions and stellar density profiles from
star counts down to very low average surface brightnesses, equivalent
to ~32 V- mag per square arcsec. These observations will provide the
definitive HST study of extra-planar stellar populations of spiral
galaxies. Our targets cover a range in galaxy mass, luminosity, and
morphology and as function of these galaxy properties we will provide:
- The first systematic study of the radial and isophotal shapes of the
diffuse stellar halos of spiral galaxies - The most detailed
comparative study to date of thick disk morphologies and stellar
populations - A comprehensive analysis of halo and thick disk
metallicity distributions as a function of galaxy type and position
within the galaxy. - A sensitive search for tidal streams - The first
opportunity to directly relate globular cluster systems to their field
stellar population We will use these fossil records of the galaxy
assembly process preserved in the old stellar populations to test halo
and thick disk formation models within the hierarchical galaxy
formation scheme. We will test LambdaCDM predictions on sub-galactic
scales, where it is difficult to test using CMB and galaxy redshift
surveys, and where it faces its most serious difficulties.

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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10558 - REACQ(2,1,2) fails during LOS

Upon acquisition of signal at 10:38:40, QF2STOPF and QSTOP flags were
set and vehicle was in gyro control. REACQ(2,1,2) at 09:44:49 failed,
primary GSACQ(2,1,2) at 08:13:58 was successful. Further information
after engineering recorder dump.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

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

SIGNIFICANT EVENTS: (None)