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 (D<3.5Mpc) 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)