Status Report

NASA Hubble Space Telescope Daily Report #4834

By SpaceRef Editor
April 16, 2009
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Continuing to collect World Class Science

PERIOD COVERED: 5am April 15 – 5am April 16, 2009 (DOY


ACS/SBC 11980
Deep FUV Imaging of Cooling Flow Clusters
We propose to take deep ACS FUV images of a carefully selected sample
of 19 bright central galaxies in nearby galaxy clusters. This program
is the last critical element of a comprehensive investigation of the
impact of stellar and AGN feedback on the local galaxy cluster
environment. The HST images will complement new, high-resolution,
Halpha images obtained with the recently commissioned
Maryland-Magellan Tunable Filter (MMTF) on the Baade 6.5m telescope,
archival Chandra, VLA, and GALEX data, and on-going H2/NIR
observations. The MMTF data have revealed unsuspected filamentary
complexes in several systems. The GALEX data often show hints of
extended NUV and FUV emission on a similar scale, but their poor
spatial resolution prevents meaningful comparison with the MMTF data.
The HST data will provide this much needed gain in resolution. The
combined radio-H2-Halpha-FUV-X-ray dataset will allow us to derive
with unprecedented precision the role of the AGN, hot stars, shocks,
and relativistic particles on the excitation and thermodynamics of the
multi-phase intracluster and interstellar media in these systems. This
is an important question since the formation and evolution of most
cluster galaxies have likely been affected by these processes.

ACS/SBC 11982
Spanning the Reionization History of IGM Helium: a Large and Efficient
HST Spectral Survey of Far-UV-Bright Quasars

The reionization of IGM helium is thought to have occurred at
redshifts of z=3 to 4. Detailed studies of HeII Lyman-alpha absorption
toward a handful of QSOs at 2.72.8 SDSS DR7 (and other) quasars with GALEX GR4 UV sources
to obtain 550 new, high confidence, sightlines potentially useful for
HST HeII studies; and in cycle 15-16 trials we demonstrated the
efficacy of our SDSS/GALEX selection approach identifying 9 new HeII
quasars at unprecedented 67% efficiency. We propose the first
far-UV-bright HeII quasar survey that is both large in scale and also
efficient, via 2-orbit reconnaissance ACS/SBC prism spectra toward a
highly select subset of 40 new SDSS/GALEX quasars at 3.14), enabling superb
post-SM4 follow-up spectra with COS or STIS. But simultaneously and
independent of any SM4 uncertainties, we will hereby directly obtain
10-orbit UV spectral stacks from the 5 HeII quasars in each of the 8
redshift bins to trace the reionization history of IGM helium over at
least 3.1 FGS 11298
Calibrating Cosmological Chronometers: White Dwarf Masses
We propose to use HST/FGS1R to determine White Dwarf {WD} masses. The
unmatched resolving power of HST/FGS1R will be utilized to follow up
four selected WD binary pairs. This high precision obtained with
HST/FGS1R simply cannot be equaled by any ground based technique. This
proposed effort complements that done by CoI Nelan in which a sample
of WDs is being observed with HST/FGS1R. This proposal will
dramatically increase the number of WDs for which dynamical mass
measurements are possible, enabling a better calibration of the WD
mass-radius relation, cooling curves, initial to final mass relations,
and ultimately giving important clues to the star formation history of
our Galaxy and the age of its disk as well as in other galaxies. {This
project is part of Subasavage’s PhD thesis work at Georgia State

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

WFPC2 11113
Binaries in the Kuiper Belt: Probes of Solar System Formation and

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

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.

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
HSTARS: (None)
FGS GSAcq 06 06
FGS REAcq 08 08
OBAD with Maneuver 28 28

SpaceRef staff editor.