Daily Report #4799

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT****** #4799

PERIOD COVERED: 5am February 25 - 5am February 26, 2009 (DOY
*************************** 056/1000z-057/1000z)

OBSERVATIONS SCHEDULED

FGS 11943

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries
among some of the most massive, least massive, and oldest stars in our
part of the Galaxy. FGS allows us to spatially resolve binary systems
that are too faint for ground-based, speckle or optical long baseline
interferometry, and too close to resolve with AO. We propose a
SNAP-style program of single orbit FGS TRANS mode observations of very
massive stars in the cluster NGC 3603, luminous blue variables, nearby
low mass main sequence stars, cool subdwarf stars, and white dwarfs.
These observations will help us to (1) identify systems suitable for
follow up studies for mass determination, (2) study the role of
binaries in stellar birth and in advanced evolutionary states, (3)
explore the fundamental properties of stars near the main
sequence-brown dwarf boundary, (4) understand the role of binaries for
X-ray bright systems, (5) find binaries among ancient and nearby
subdwarf stars, and (6) help calibrate the white dwarf mass - radius
relation.

WFPC2 11161

Revealing the Explosion Geometry of Nearby GRB-SNe

The connection between gamma-ray bursts and Type Ibc supernovae is
well-established in broad terms. However, our recent identification of
an intermediate class of sub-energetic GRBs, and the overall overlap
in Nickel production between GRB-SNe and ordinary SNe Ibc suggest that
the properties leading to the production of a relativistic engine are
yet to be uncovered. A fundamental difference between the two classes
of explosions may be imprinted in the overall geometry of the
explosion. The relativistic component of GRBs is known to be highly
collimated, but it is unclear if the SN blast is spherical or mildly
collimated as well. Here we propose HST observations of the late (30
days) decay tails of two GRB-SNe as an independent measure of the
Nickel mass synthesized in the explosion. A comparison to the Nickel
mass inferred from the peak brightness of the SNe will provide a
direct measure of the explosion asymmetry, since at late time the
explosion is essentially spherical. These observations will form the
core of a multi-wavelength (optical, X-ray, radio) effort to fully
characterize all aspects of the explosions, from the energy and
geometry of the relativistic material (VLA, Chandra) to the early SN
evolution (Keck, Magellan). The proposed observations require two
slow-response (30 days) TOOs, ideally suited to the 2-gyro operations
of HST.

WFPC2 11974

High-resolution Imaging for 9 Very Bright, Spectroscopically
Confirmed, Group-scale Lenses

There are large samples of strong lenses that probe small (galaxy)
scale masses (e.g., SLACS, SQLS, COSMOS). There are also large samples
of strong lenses that probe large (rich cluster) scale masses (e.g.,
various rich Abell clusters, the Hennawi et al. 2008 SDSS sample). The
sample of strong lenses that probe intermediate (group/cluster-core)
scale masses, however, is sparse, and so any significant additions to
this sample are important. Here we present a sample of strong lenses
that not only probe these intermediate scales but are also quite
bright, since the sample is based almost entirely upon data from the
SDSS, a relatively shallow and poor-resolution survey, at least in
comparison to most other strong lens hunting grounds, such as COSMOS
and CFHTLS. What we lack are the high-resolution imaging data needed
to construct detailed lensing models, to probe the mass and light
profiles of the lensing galaxies and their environments, and to
characterize the morphologies of the lensed (source) galaxies. Only
HST can provide these data, and so we are proposing here for 81 orbits
of deep WFPC2 F450W, F606W and F814W imaging, for 9 of our best and
brightest intermediate-scale lensing systems with known spectroscopic
redshifts and with Einstein radii between 4 and 8 arcsec.

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

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************** 06**************** 06
FGS REAcq************** 08**************** 08
OBAD with Maneuver **** 28**************** 28

SIGNIFICANT EVENTS: (None)