Notice: Due to the conversion of some ACS WFC or HRC observations into
WFPC2, or NICMOS observations after the loss of ACS CCD science
capability in January, there may be an occasional discrepancy between a
proposal's listed (and correct) instrument usage and the abstract that
follows it.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4442

PERIOD COVERED: UT September 06, 2007 (DOY 249)

OBSERVATIONS SCHEDULED

WFPC2 11034

WFPC2 Closeout Photometric Characterization

The standard star GRW+70D5829 is observed in filter and chip
combinations that were not included in photometric calibration programs
from 2005, 2006, and 2007. These observations are needed to complete a
library of recent standard star observations taken in all filter and
chip combinations before WFPC2 is decommissioned in SM4. {Linear Ramp
and Polarizer filters are covered in a separate proposal.} These
observations, along with other recent standard star observations, will
be used to study long-term throughput.

WFPC2 11038

Narrow Band and Ramp Filter Closeout

These observations are to improve calibration of narrow band and ramp
filters. We also test for changes in the filter properties during
WFPC2's 14 years on-board HST.

WFPC2 11084

Probing the Least Luminous Galaxies in the Local Universe

We propose to obtain deep color-magnitude data of eight new Local Group
galaxies which we recently discovered: Andromeda XI, Andromeda XII, and
Andromeda XIII {satellites of M31}; Canes Venatici I, Canes Venatici II,
Hercules, and Leo IV {satellites of the Milky Way}; and Leo T, a new
"free-floating" Local Group dwarf spheroidal with evidence for recent
star formation and associated H I gas. These represent the least
luminous galaxies known at *any* redshift, and are the only accessible
laboratories for studying this extreme regime of galaxy formation. With
deep WFPC-2 F606W and F814W pointings at their centers, we will
determine whether these objects contain single or multiple age stellar
populations, as well as whether these objects display a range of
metallicities.

WFPC2 11100

Two new `bullets' for MOND: revealing the properties of dark matter in
massive merging clusters

The principal objective of this proposal is to study the physical nature
of dark matter by using two, massive, newly-identified merging clusters
of galaxies. As shown by the pioneering example of the ``bullet
cluster'' {1E0657-56}, such systems are ideal laboratories for detecting
dark matter and distinguishing between cold dark matter {CDM} and other
scenarios {e.g. self-interacting dark matter}. Our limit on the
self-interaction cross-section of dark matter relies on the assumption
of a normal pre-merger mass-to-light ratios, and a small impact
parameter during the collision of the two clusters. In order to mitigate
any possible systematic effects, it is vital to extend this work to
other, similar systems. With detailed observations of new systems, the
systematic uncertainties in the dark matter cross section calculations
can be improved substantially, allowing us to move from rough order of
magnitude estimates to measurements with quantifiable uncertainties that
can be compared usefully with the predictions from numerical
simulations. Our targets are two extraordinary, high-redshift, merging
galaxy clusters recently discovered by the Massive Cluster Survey
{MACS}. This survey is by far the best matched to this study, since it
selects medium redshift {optimal for gravitational lensing studies} and
X-ray luminous {hence massive} objects. We have selected the best
candidates with clear evidence for considerable offsets between the hot
X-ray emitting gas and optically luminous stellar material. The two most
striking examples are the targets of this proposal. To pin down the
position of the dark matter component we require high resolution,
absolutely calibrated mass maps. The combination of weak and strong
lensing measurements is needed to attain this goal. This can only be
achieved with the excellent resolving power of the HST {in combination
with wide-field, multicolor Subaru data already in hand}. We therefore
request multicolor HST/WFPC2 observations of the two merging clusters.
The combination of constraints from multiply lensed images {identified
via morphology and color information} and high-resolution weak lensing
data will allow us to construct, self-consistently, their mass
distribution from the very centers to the outskirts. Gravitational
lensing thus provides a unique tool transforming these clusters into
dark matter laboratories. They will supply us with answers as to the
nature and properties of dark matter, and how it shapes galaxies and
galaxy clusters and their evolution through cosmic time.

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               05                 05                     
FGS REacq               08                 08                  
OBAD with Maneuver 26                 26              

SIGNIFICANT EVENTS: (None)