Notice:
Due to the conversion of some ACS WFC or HRC observations into
WFPC2,
or NICMOS observations after the loss of ACS CCD science
capability
in January, there may be an occasional discrepancy between a
proposal's
listed (and correct) instrument usage and the abstract that
follows
it.
HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4436
PERIOD
COVERED: UT August 28, 2007 (DOY 240)
OBSERVATIONS
SCHEDULED
WFPC2
10599
Multi-color
imaging of two 1 Gyr old debris disks within 20 pc of the
Sun:
Astrophysical mirrors of our Kuiper Belt
We
report the first scattered light detections of two debris disk around
an
F star and a K star using optical coronagraphy and the Hubble Space
Telescope.
With ages ~1 Gyr, these are the oldest debris disks thus far
seen
in the optical. We propose deep, multi-roll angle coronagraphic
imaging
with HST ACS and NICMOS to confirm and characterize the disks in
terms
of structure and composition. The disks appear to have belt-like
morphology
that is consistent with the existence of planetary companions
or
other perturbing bodies. Since these disks are close to our Kuiper
Belt
in an evolutionary context, detailed understanding of their mass,
structure
and composition will provide a fresh perspective for inferring
the
history and properties of our own trans-Neptunian region.
WFPC2
10915
ACS
Nearby Galaxy Survey
Existing
HST observations of nearby galaxies comprise a sparse and
highly
non-uniform archive, making comprehensive comparative studies
among
galaxies essentially impossible. We propose to secure HST's
lasting
impact on the study of nearby galaxies by undertaking a
systematic,
complete, and carefully crafted imaging survey of ALL
galaxies
in the Local Universe outside the Local Group. The resulting
images
will allow unprecedented measurements of: {1} the star formation
history
{SFH} of a >100 Mpc^3 volume of the Universe with a time
resolution
of Delta[log{t}]=0.25; {2} correlations between spatially
resolved
SFHs and environment; {3} the structure and properties of thick
disks
and stellar halos; and {4} the color distributions, sizes, and
specific
frequencies of globular and disk clusters as a function of
galaxy
mass and environment. To reach these goals, we will use a
combination
of wide-field tiling and pointed deep imaging to obtain
uniform
data on all 72 galaxies within a volume-limited sample extending
to
~3.5 Mpc, with an extension to the M81 group. For each galaxy, the
wide-field
imaging will cover out to ~1.5 times the optical radius and
will
reach photometric depths of at least 2 magnitudes below the tip of
the
red giant branch throughout the limits of the survey volume. One
additional
deep pointing per galaxy will reach SNR~10 for red clump
stars,
sufficient to recover the ancient SFH from the color-magnitude
diagram.
This proposal will produce photometric information for ~100
million
stars {comparable to the number in the SDSS survey} and uniform
multi-
color images of half a square degree of sky. The resulting
archive
will establish the fundamental optical database for nearby
galaxies,
in preparation for the shift of high- resolution imaging to
the
near-infrared.
WFPC2
11030
WFPC2
WF4 Temperature Reduction #3
In
the fall of 2005, a serious anomaly was found in images from the WF4
CCD
in WFPC2. The WF4 CCD bias level appeared to have become unstable,
resulting
in sporadic images with either low or zero bias level. The
severity
and frequency of the problem was rapidly increasing, making it
possible
that WF4 would soon become unusable if no work-around were
found.
Examination of bias levels during periods with frequent WFPC2
images
showed low and zero bias episodes every 4 to 6 hours. This
periodicity
is driven by cycling of the WFPC2 Replacement Heater, with
the
bias anomalies occurring at the temperature peaks. The other three
CCDs
{PC1, WF2, and WF3} appear to be unaffected and continue to operate
properly.
Lowering the Replacement Heater temperature set points by a
few
degrees C effectively eliminates the WF4 anomaly. On 9 January 2006,
the
upper set point of the WFPC2 Replacement Heater was reduced from
14.9C
to 12.2C. On 20 February 2006, the upper set point was reduced
from
12.2C to 11.3C, and the lower set point was reduced from 10.9C to
10.0C.
These changes restored the WF4 CCD bias level; however, the bias
level
has begun to trend downwards again, mimicking its behavior in late
2004
and early 2005. A third temperature reduction is planned for March
2007.
We will reduce the upper set point of the heater from 11.3C to
10.4C
and the lower set point from 10.0C to 9.1C. The observations
described
in this proposal will test the performance of WFPC2 before and
after
this temperature reduction. Additional temperature reductions may
be
needed in the future, depending on the performance of WF4. Orbits:
internal
26, external 1
WFPC2
11033
Full
Moon Earth Flats Closeout
Flat
field exposures will be obtained by observing the moonlit Earth
with
the broadband WFPC2 filters F606W and F814W, which saturate in the
minimum
exposure time on the sunlit Earth. These observations will be
used
to improve the flats currently in the pipeline and are part of the
WFPC2
closeout operations. Because CTE effects are large for star flats
and
small for full field illumination, Earth flats are the superior
technique.
WFPC2
11113
Binaries
in the Kuiper Belt: Probes of Solar System Formation and
Evolution
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 impact.
WFPC2
11218
Snapshot
Survey for Planetary Nebulae in Globular Clusters of the Local
Group
Planetary
nebulae {PNe} in globular clusters {GCs} raise a number of
interesting
issues related to stellar and galactic evolution. The number
of
PNe known in Milky Way GCs, 4, is surprisingly low if one assumes
that
all stars pass through a PN stage. However, it is likely that the
remnants
of stars now evolving in Galactic GCs leave the AGB so slowly
that
any ejected nebula dissipates long before the star becomes hot
enough
to ionize it. Thus there should not be ANY PNe in Milky Way
GCs--but
there are four! It has been suggested that these PNe are the
result
of mergers of binary stars within GCs, i.e., that they are
descendants
of blue stragglers. The frequency of occurrence of PNe in
external
galaxies poses more questions, because it shows a range of
almost
an order of magnitude. I propose a Snapshot survey aimed at
discovering
PNe in the GC systems of Local Group galaxies more distant
than
the Magellanic Clouds. These clusters, some of which may be much
younger
than their counterparts in the Milky Way, might contain many
more
PNe than those of our own galaxy. I will use the standard technique
of
emission-line and continuum imaging, which easily discloses PNe.
WFPC2
11289
SL2S:
The Strong Lensing Legacy Survey
Recent
systematic surveys of strong galaxy-galaxy lenses {CLASS, SLACS,
GOODS,
etc.} are producing spectacular results for galaxy masses roughly
below
a transition mass M~10^13 Mo. The observed lens properties and
their
evolution up to z~0.2, consistent with numerical simulations, can
be
described by isothermal elliptical potentials. In contrast, modeling
of
giant arcs in X-ray luminous clusters {halo masses M >~10^13 Mo}
favors
NFW mass profiles, suggesting that dark matter halos are not
significantly
affected by baryon cooling. Until recently, lensing
surveys
were neither deep nor extended enough to probe the intermediate
mass
density regime, which is fundamental for understanding the assembly
of
structures. The CFHT Legacy Survey now covers 125 square degrees, and
thus
offers a large reservoir of strong lenses probing a large range of
mass
densities up to z~1. We have extracted a list of 150 strong lenses
using
the most recent CFHTLS data release via automated procedures.
Following
our first SNAPSHOT proposal in cycle 15, we propose to
continue
the Hubble follow-up targeting a larger list of 130 lensing
candidates.
These are intermediate mass range candidates {between
galaxies
and clusters} that are selected in the redshift range of 0.2-1
with
no a priori X-ray selection. The HST resolution is necessary for
confirming
the lensing candidates, accurate modeling of the lenses, and
probing
the total mass concentration in galaxy groups up to z~1 with the
largest
unbiased sample available to date.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
10963
- GSAcq(1,2,1) results in Fine Lock Back-up (1,0,1)
GSAcq (1,2,1) scheduled at 241/06:40:56 resulted in Fine Lock
Back-up
(1,0,1) using FGS 1.
OBAD #1 RSS: 2125.80
OBAD #2 RSS: 7.20
OBAD MAP RSS:
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
07
07
FGS
REacq
05
05
OBAD
with Maneuver 24
24
SIGNIFICANT
EVENTS: (None)