Status Report

NASA Hubble Space Telescope Daily Report #4838

By SpaceRef Editor
April 22, 2009
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: 5am April 21 – 5am April 22, 2009 (DOY


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

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.


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be


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.




FGS GSAcq 09 08
FGS REAcq 05 05
OBAD with Maneuver 22 21


SpaceRef staff editor.