HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4838
PERIOD COVERED: 5am April 21 - 5am April 22, 2009 (DOY
111/0900z-112/0900z)
OBSERVATIONS SCHEDULED
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 11975
UV Light from Old Stellar Populations: a Census of UV
Sources in
Galactic Globular Clusters
In spite of the fact that HST has been the only operative
high-resolution eye in the UV-window over the last 18
years, no
homogeneous UV survey of Galactic globular clusters (GGCs)
has been
performed to date. In order to fill this gap in the
stellar population
studies, we propose a program that exploits the unique
capability of the
WFPC2 and the SBC in the far-/mid- UV for securing deep UV
imaging of 46
GGCs. The proposed observations will allow to study with
unprecedented
accuracy the hottest GGC stars, comprising the extreme
horizontal branch
(HB) stars and their progeny (the so-called AGB-manque',
and Post-early
AGB stars), and "exotic stellar populations"
like the blue straggler
stars and the interacting binaries. The targets have been
selected to
properly sample the GGC metallicity/structural parameter
space, thus to
unveil any possible correlation between the properties of
the hot
stellar populations and the cluster characteristics. In
addition, most
of the targets have extended HB "blue tails", that
can be properly
studied only by means of deep UV observations, especially
in the far-UV
filters like the F160BW, that is not foreseen on the WFC3.
This data
base is complemented with GALEX observations in the
cluster outermost
regions, thus allowing to investigate any possible trend
of the
UV-bright stellar types over the entire radial extension
of the
clusters. Although the hottest GGC stars are just a small
class of
"special" objects, their study has a broad
relevance in the context of
structure formation and chemical evolution in the early
Universe,
bringing precious information on the basic star formation
processes and
the origin of blue light from galaxies. Indeed, the
proposed
observations will provide the community with an
unprecedented data set
suitable for addressing a number of still open
astrophysical questions,
ranging from the main drivers of the HB morphology and the
mass loss
processes, to the origin of the UV upturn in elliptical
galaxies, the
dating of distant systems from integrated light, and the
complex
interplay between stellar evolution and dynamics in dense
stellar
aggregates. In the spirit of constructing a community
resource, we
entirely waive the proprietary period for these
observations.
WFPC2 11979
WFPC2 Imaging of Fomalhaut b: Determining its Orbit and
Testing for
H-alpha Emission
Fomalhaut is a bright nearby star that harbors a belt of
dusty material
with a morphology that has been used to predict the
presence of a
shepherding planet. With ACS/HRC coronagraphy, we have
achieved the
direct detection of a planet candidate (Fomalhaut b) in
F606W and F814W.
The planet candidate lies 18 AU interior to the dust belt
and we detect
counterclockwise orbital motion in two epochs of
observations (2004 and
2006). Fomalhaut b has mass no greater than three Jupiter
masses based
on an analysis of its luminosity, including non-detections
at infrared
wavelengths, and the dynamical argument that a
significantly more
massive object would disrupt the dust belt. Variability at
optical
wavelengths and the brightness in the F606W passband
suggest additional
sources of luminosity such as starlight reflected from a
circumplanetary
ring system. A second possibility that has been invoked
for substellar
objects is a significant contribution of H-alpha emission.
Here we
propose follow-up WFPC2 observations to test the
possibility that the
F606W flux is contaminated by H-alpha emission. We
demonstrate that the
detection of Fomalhaut b using WFPC2 is feasible using
roll
deconvolution. Furthermore, a detection of Fomalhaut b in
2009 will
provide a crucial third epoch for astrometry. With the
existing two
epochs of data, the orbit of Fomalhaut b cannot be
determined uniquely.
The third epoch will be used to test the prediction of
apsidal alignment
and more accurately determine the dynamical mass of
Fomalhaut b. If
apsidal mis-alignment is found between the planet and the
belt, this
result would point to the existence of still other planets
lurking
unseen in the Fomalhaut system.
WFPC2 11981
FUV Imaging Survey of Galactic Open Clusters
We propose a WFPC2 FUV imaging survey of 6 Galactic open
clusters with
ages ranging from 1 Myr to 300 Myr complemented with
NUV/optical imaging
of the same fields. No such survey has ever been attempted
before in the
FUV at the resolution of WFPC2 (indeed, no WFPC2 FUV
images of any
Galactic open cluster exist in the HST archive) and, since
WFPC2 will be
retired in SM4 and none of the other HST instruments can
do FUV imaging
of bright objects, this is the last chance to do such a
survey before
another UV telescope is launched. This survey will provide
a new
perspective on young/intermediate age Galactic clusters
and a key
template for the study of star formation at high redshift,
where the
intensity peak we observe in the optical/NIR from Earth is
located in
the FUV in its rest frame. For clusters still associated
with an H II
region, UV imaging maps the continuum emission of the
ionized gas and
the radiation scattered by background dust and, combined
with optical
nebular images, can be used to determine the 3-D structure
of the H II
region. For all young clusters, FUV+NUV+optical photometry
can be used
to study the UV excesses of T-Tauri stars. For clusters
older than ~40
Myr, the same photometric combination is the easiest
method to detect
companion white dwarfs which are invisible using only the
optical and
NIR. WFPC2 is also an excellent instrument to discover
close companions
around bright stars and improve our knowledge of their multiplicity
fraction. Finally, for all clusters, the combination of
high-spatial-resolution UV and optical photometry can be
used to
simultaneously measure the temperature, extinction,
extinction law,
distance, and existence of companions (resolved and unresolved)
and,
thus, produce clean HR diagrams with resolved cluster
membership and
much-reduced systematic uncertainties.
WFPC2 11983
An Imaging Survey of Protoplanetary Disks and Brown Dwarfs
in the
Chamaeleon I Region
We propose to carry out a HST/WFPC2 survey of young brown
dwarfs, Class
I and Class II sources in the Chamaelon I region, one of
the
best-studied star-forming regions, in order to investigate
the link
between disk evolution and the formation of
substellar-mass objects. We
will use deep broad-band imaging in the I and z-equivalent
HST bands to
unveil the unknown population of substellar binary
companions, down to a
few Jupiter masses for separations of a few tens of AU. We
will also
perform narrow-band imaging to directly detect accreting
circumstellar
disks and jets around brown dwarfs, Class-I and class-II
objects.
Chamaelon I is nearly coeaval of Orion (~1-2Myr) but at
~1/3 its
distance, allowing 3x higher resolution and 10x more flux
for comparable
objects. Unlike Orion, low-mass objects and protoplanetary
disks in
Chamaeleon I have been extensively studied with Spitzer,
but not yet
with the HST. The Chamaeleon I region is an ideal HST
target, as it lies
in the CVZ of the HST and therefore it is easily
accessible any time of
the year with long orbits.
WFPC2 11993
High Resolution Imaging of a Binary Supermassive Black
Hole Candidate
Dithered high resolution images of a supermassive binary
black hole
candidate SDSS J153636.22+044127.0 will be obtained with
the WFPC2/PC in
F675W. This QSO was identified in November, 2008 by a
principal
components analysis of the ~ 17, 500 QSOs in the SDSS DR7
sample. It is
unique among all known QSOs in having two broadline
regions, indicative
of two supermassive black holes being actively fed. It is
the best
candidate for a supermassive binary black hole known. Such
binaries
should be common in the Universe and play key roles in the
formation and
evolution of galaxies, yet no convincing examples had been
identified
prior to this QSO. The HST imaging should be able to
constrain two
alternative hypotheses that this object is 1) the site of
a black hole
ejected from a nucleus by a multi-body interaction, or 2)
a simple line
of sight superposition of two unrelated AGN. With the superb
spatial
resolution of HST, two AGN separated by > 300pc
(projected) should be
readily visible.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be investigated.)
HSTARS:
11778 - GSAcq(2,1,1) scheduled at 112/06:48:30 failed at
112/06:52:40 due to
search radius limit exceeded on FGS1.
Observations affected: WFPC 141 - 148, Proposal ID# 11983.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
09
08
FGS REAcq
05
05
OBAD with Maneuver
22
21
SIGNIFICANT EVENTS: None