Status Report

NASA Hubble Space Telescope Daily Report #4832

By SpaceRef Editor
April 14, 2009
Filed under , ,


Continuing to collect World Class Science

PERIOD COVERED: 5am April 13 – 5am April 14, 2009 (DOY


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

WFPC2 11302

WFPC2 CYCLE 16 Standard Darks – Part III
This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

WFPC2 11793

WFPC2 Cycle 16 Internal Monitor
This calibration proposal is the Cycle 15 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A
variety of internal exposures are obtained in order to provide a
monitor of the integrity of the CCD camera electronics in both bays
(both gain 7 and gain 15 — to test stability of gains and bias
levels), a test for quantum efficiency in the CCDs, and a monitor for
possible buildup of contaminants on the CCD windows. These also
provide raw data for generating annual super-bias reference files for
the calibration pipeline.

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 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 11978

Luminous and Dark Matter in Disk Galaxies from Strong Lensing and
Stellar Kinematics
The formation of realistic disk galaxies within the LCDM paradigm is
still an unsolved problem. Theory is only now beginning to make
predictions for how dark matter halos respond to galaxy formation and
for the properties of disk galaxies. Measuring the density profiles of
dark matter halos on galaxy scales is therefore a strong test for the
standard paradigm of galaxy formation, offering great potential for
discovery. However, from an observational point of view, the
degeneracy between the stellar and dark matter contributions to galaxy
rotation curves remains a major road block. Strong gravitational
lensing, when coupled to spatially-resolved kinematics and stellar
population models, can solve this long-standing problem.
Unfortunately, this joint methodology could not be exploited so far
due to the paucity of known edge-on spiral lenses. Exploiting the full
SDSS-DR7 archive we have identified a new sample of exactly these
systems. We propose multi-color HST imaging to confirm and measure a
sample of twenty spiral lenses, covering a range of bulge to disk
ratios. By combining dynamical lensing and stellar population
information for this unique sample we will deliver the first
statistical constraints on halos and disk properties, and a new
stringent test of disk galaxy formation theories.


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

HSTARS: (None)
FGS GSAcq 04 04
FGS REAcq 09 09
OBAD with Maneuver 26 26

SpaceRef staff editor.