HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4820
PERIOD COVERED: 5am March 26 - 5am March 27, 2009 (DOY
085/0900z-086/0900z)
OBSERVATIONS SCHEDULED
WFPC2 10877
A Snapshot Survey of the Sites of Recent, Nearby Supernovae
During the past few years, robotic {or nearly robotic} searches for
supernovae {SNe}, most notably our Lick Observatory Supernova Search
{LOSS}, have found hundreds of SNe, many of them in quite nearby
galaxies {cz < 4000 km/s}. Most of the objects were discovered before
maximum brightness, and have follow-up photometry and spectroscopy; they
include some of the best-studied SNe to date. We propose to conduct a
snapshot imaging survey of the sites of some of these nearby objects, to
obtain late-time photometry that {through the shape of the light and
color curves} will help reveal the origin of their lingering energy. The
images will also provide high-resolution information on the local
environments of SNe that are far superior to what we can procure from
the ground. For example, we will obtain color-color and color-magnitude
diagrams of stars in these SN sites, to determine the SN progenitor
masses and constraints on the reddening. Recovery of the SNe in the new
HST images will also allow us to actually pinpoint their progenitor
stars in cases where pre- explosion images exist in the HST archive.
This proposal is an extension of our successful Cycle 13 snapshot survey
with ACS. It is complementary to our Cycle 15 archival proposal, which
is a continuation of our long-standing program to use existing HST
images to glean information about SN environments.
ACS/SBC 11791
The Wavelength Dependence of Accretion Disk Structure
We can now routinely measure the size of quasar accretion disks using
gravitational microlensing of lensed quasars. The next step to testing
accretion disk models is to measure the size of accretion disks as a
function of wavelength, particularly at the UV and X-ray wavelengths
that should probe the inner, strong gravity regime. Here we focus on two
four-image quasar lenses that already have optical (R band) and X-ray
size measurements using microlensing. We will combine the HST
observations with ground-based monitoring to measure the disk size as a
function of wavelength from the near-IR to the UV. We require HST to
measure the image flux ratios in the ultraviolet continuum near the
Lyman limit of the quasars. The selected targets have estimated black
hole masses that differ by an order of magnitude, and we should find
wavelength scalings for the two systems that are very different because
the Blue/UV wavelengths should correspond to parts of the disk near the
inner edge for the high mass system but not in the low mass system. The
results will be modeled using a combination of simple thin disk models
and complete relativistic disk models. While requiring only 18 orbits,
success for one system requires observations in both Cycles 16 and 17.
WFPC2 11113
Binaries in the Kuiper Belt: Probes of Solar System Formation and
Evolution
The discovery of binaries in the Kuiper Belt and related small body
populations is powering a revolutionary step forward in the study of
this remote region. Three quarters of the known binaries in the Kuiper
Belt have been discovered with HST, most by our snapshot surveys. The
statistics derived from this work are beginning to yield surprising and
unexpected results. We have found a strong concentration of binaries
among low-inclination Classicals, a possible size cutoff to binaries
among the Centaurs, an apparent preference for nearly equal mass
binaries, and a strong increase in the number of binaries at small
separations. We propose to continue this successful program in Cycle 16;
we expect to discover at least 13 new binary systems, targeted to
subgroups where these discoveries can have the greatest impact.
WFPC2 11944
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 11972
Investigating the Early Solar System with Distant Comet Nuclei
We propose 85 orbits of imaging observations with the WFPC2 to get
nucleus size estimates for 8 well observed dynamically new and
long-period comets at large distances from the sun when their activity
levels are low. This will increase the sample of these nucleus sizes by
nearly 50%, but will more than double the selection of comets for which
we can run thermal models. Small icy bodies are the best preserved
remnants of planet formation, and we have recently found that
observationally constrained thermal models can distinguish differences
in microphysical properties of comet nuclei. The new HST data will
enable the first exploration of physical conditions in different regions
of the early solar nebula.
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 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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports
of potential non-nominal performance that will be investigated.)
HSTARS:
11741 - GSAcq (1,3,1) scheduled @085/11:15:43z resulted in Fine Lock
Back-up (1,0,1)
@ 085/11:26:05z
Observations possibly
affected: ACS #2, Proposal ID #11791
11742 - GSAcq (1,2,2) scheduled @85/21:15:48z failed to RGA Control during LOS.
Observations
affected: WFPC #149-150, Proposal ID #11974.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS GSAcq
06
05
FGS REAcq
07
07
OBAD with Maneuver 26
26
SIGNIFICANT EVENTS: (None)