HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4795
PERIOD COVERED: 5am February 19 - 5am February 20, 2009
(DOY
050/1000z-051/1000z)
OBSERVATIONS SCHEDULED
WFPC2 11590
Observing the IR Catastrophe in a Deflagration
Our lack of understanding of
our confidence in their use for cosmology. While there is
broad
agreement that these objects represent the explosions of
white dwarfs,
the details of the explosion mechanism are not
well-understood.
Recently, we have identified an internally homogeneous
subclass of SNe
Ia whose photometric and spectroscopic peculiarities make
them quite
distinct from normal SNe Ia. Models suggest we may be
seeing the result
of an explosion with a subsonic burning front, called a
deflagration. We
propose to test SN Ia models by obtaining late-time
photometry for SN
2008A, a recent, nearby example of this subclass, using
ACS and WFC3 on
HST. We will accurately measure the late-time photometric
decline rate
and spectral energy distribution (SED). These observations
will allow us
to test whether the ejecta contain the large amount of
oxygen predicted
by certain models. We also aim to detect major evolution
of the SED
expected due to the "IR catastrophe, " a change
in the dominant cooling
mechanism in the ejecta, as generically predicted by
models but only
hinted at by current observations.
FGS 11944/11943
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 to observe using 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 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 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:
#11688 REAcq (2,1,2) Loss of Lock while guiding under two
FGS during LOS @050/17:25z
Observations possibly affected: WFPC #117-118, Proposal ID #11986.
COMPLETED OPS REQUEST: None
COMPLETED OPS NOTES:
None
SCHEDULED SUCCESSFUL
FAILURE TIME
FGS
GSAcq
06
06
FGS
REAcq
07
07
OBAD with Maneuver
26
26
LOSS of
LOCK
050/17:25z
SIGNIFICANT EVENTS: (None)