Daily Report #4813

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT****** #4813

PERIOD COVERED: 5am March 17 - 5am March 18, 2009 (DOY
*************************** 076/0900z-077/0900z)

OBSERVATIONS SCHEDULED

WFPC2 11978

Luminous and Dark Matter in Disk Galaxies from Strong Lensing and
Stellar Kinematics

The formation of realistic disk galaxies within the LCDM paradigm is
still an unsolved problem. Theory is only now beginning to make
predictions for how dark matter halos respond to galaxy formation and
for the properties of disk galaxies. Measuring the density profiles of
dark matter halos on galaxy scales is therefore a strong test for the
standard paradigm of galaxy formation, offering great potential for
discovery. However, from an observational point of view, the
degeneracy between the stellar and dark matter contributions to galaxy
rotation curves remains a major road block. Strong gravitational
lensing, when coupled to spatially-resolved kinematics and stellar
population models, can solve this long-standing problem.
Unfortunately, this joint methodology could not be exploited so far
due to the paucity of known edge-on spiral lenses. Exploiting the full
SDSS-DR7 archive we have identified a new sample of exactly these
systems. We propose multi-color HST imaging to confirm and measure a
sample of twenty spiral lenses, covering a range of bulge to disk
ratios. By combining dynamical lensing and stellar population
information for this unique sample we will deliver the first
statistical constraints on halos and disk properties, and a new
stringent test of disk galaxy formation theories.

WFPC2 11986

Completing HST's Local Volume Legacy

Nearby galaxies offer one of the few laboratories within which stellar
populations can be tied to multi-wavelength observations. They are
thus essential for calibrating and interpreting key astrophysical
observables, such as broad-band luminosities, durations and energy
input from starbursts, and timescales of UV, H-alpha, and FIR
emission. The study of stellar populations in nearby galaxies requires
high-resolution observations with HST, but HST's legacy for this
limited set of galaxies remains incomplete.

As a first attempt to establish this legacy, The ACS Nearby Galaxy
Survey Treasury (ANGST) began observations in late 2006. ANGST was
designed to carry out a uniform multi-color survey of a volume-limited
sample of ~70 nearby galaxies that could be used for systematic
studies of resolved stellar populations. The resulting data provide
nuanced constraints on the processes which govern star formation and
galaxy evolution, for a well-defined population of galaxies. All
photometry for the survey has been publicly released.

However, the failure of ACS 4.5 months after ANGST began taking data
led to a drastic reduction in the planned survey. The loss is
two-fold. First, the goals of completeness and uniformity were greatly
compromised, impacting global comparison studies. Second, the variety
of observed star formation histories was reduced. Given that we have
never found two galaxies with identical star formation histories, and
fully sampling the population allows us to catch those few systems
whose star formation rates and metallicities place the strongest
constraints on key astrophysical processes.

Here we propose WFPC2 observations of all remaining galaxies within
the Local Volume (D3.5Mpc) for which current HST observations are
insufficient for meaningful stellar population studies. We will use
these observations for research on the star formation histories of
individual galaxies and the Local Volume, detailed calibrations of
star formation rate indicators, and the durations of starbursts. We
will also make them publicly available through the ANGST archive to
support future research. The proposed observations will finally
complete a lasting legacy of HST

WFPC2 11987

The Recent Star Formation History of SINGS Galaxies

The Spitzer Legacy project SINGS provided a unique view of the current
state of star formation and dust in a sample of galaxies of all Hubble
types. This multi-wavelength view allowed the team to create current
star formation diagnostics that are independent of the dust content
and increased our understanding of the dust in galaxies. Even so,
using the SINGS data alone we can only make rough estimates of the
recent star formation history of these galaxies. The lack of U-band
observations means that it is impossible to estimate the ages of young
clusters. In addition, the low resolution of the Spitzer and
ground-based observations means that what appear to be individual
Spitzer sources can actually be composed of many individual clusters
with varying ages. In this proposal we plan to address this missing
area in SINGS by obtaining high-resolution WFPC2 UBVI observations to
accurately find and determine the ages of the young stellar clusters
in a subset of the SINGS galaxies. These observations will greatly
enhance the legacy value of the SINGS observations while also directly
answering questions pertaining to star formation in galaxies.

WFPC2 11988

Searching for Intermediate Mass Black Holes in Globular Clusters via
Proper Motions

The unambiguous detection of an intermediate mas black hole (IMBH) in
a globular star cluster would be a major achievement for the Hubble
Space Telescope. It is critical to know whether or not IMBHs exist in
the centers of clusters in order to understand the dynamical evolution
of dense stellar systems. Also, n IMBH detection would prove the
existence of BHs in an entirely new mass range. Observationally, the
search has been hampered by the low number of stars with known
velocities in the central few arcseconds. This limits measurements of
the stellar velocity dispersion in the region where the gravitational
influence of any IMBH would be felt. Existing IMBH claims i the
literature have all been called into question, and have all been based
on line-of-sight velocities from spectroscopy. In cycle 13, we
obtained ACS/HRC observations for 5 nearby Galactic globular clusters
for a new proper motion study. Here, we request WFPC2/PC observations
of these clusters, all of which are observable in Feb-May 2009. This 4
year baseline will allow us to measure the proper motions of stars
into the very center of each cluster, and either detect or place firm
constraints on the presence of an IMBH. In addition, we will determine
whether or not the clusters rotate or show any anisotropy in their
motions. Our small (75 orbit) program meets the criteria of
addressing high impact science (IMBH detection) using innovative
methods (proper motions).

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

11728 - REAcq(1,2,1) at 076/10:03:45 failed to RGA hold due to scan
step limit exceeded on FGS 1 at 10:09:34.

Observations affected: WFPC 63, Proposal ID# 11978.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

*********************** SCHEDULED***** SUCCESSFUL

FGS GSAcq************** 04***************** 04
FGS REAcq************** 09***************** 08
OBAD with Maneuver **** 20***************** 20

SIGNIFICANT EVENTS: (None)