HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4833
PERIOD COVERED: 5am April 14 - 5am April 15, 2009 (DOY
104/0900z-105/0900z)
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 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.
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
06
06
FGS REAcq
08
08
OBAD with Maneuver
28
28
SIGNIFICANT EVENTS: (None)