Daily # 4115

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4115

PERIOD COVERED: UT May 16, 2006 (DOY 136)

OBSERVATIONS SCHEDULED

ACS/HRC/WFC 10487

A Search for Debris Disks in the Coeval Beta Pictoris Moving Group

Resolved observations of debris disks present us with the opportunity
of studying planetary evolution in other solar systems. We propose to
search for debris disks in the Beta Pictoris moving group {8-20 Myrs,
10-50 pc away} , which provides a coeval sample of multiple spectral
types, and it has already produced two magnificent resolved debris
disks: AU Mic and Beta Pic. Such coeval sample will provide us with a
snapshop of the crucial time in disk evolution in which the disk makes
the transition from optically thick to optically thin, and it will be
useful to study the stellar mass dependence of the disk evolution.

ACS/HRC/WFC 10733

CCD Hot Pixel Annealing

Hot pixel annealing will continue to be performed once every 4 weeks.
The CCD TECs will be turned off and heaters will be activated to bring
the detector temperatures to about +20C. This state will be held for
approximately 6 hours, after which the heaters are turned off, the
TECs turned on, and the CCDs returned to normal operating condition.
To assess the effectiveness of the annealing, a bias and four dark
images will be taken before and after the annealing procedure for both
WFC and HRC. The HRC darks are taken in parallel with the WFC darks.
The charge transfer efficiency {CTE} of the ACS CCD detectors declines
as damage due to on-orbit radiation exposure accumulates. This
degradation has been closely monitored at regular intervals, because
it is likely to determine the useful lifetime of the CCDs. We combine
the annealling activity with the charge transfer efficiency monitoring
and also merge into the routine dark image collection. To this end,
the CTE monitoring exposures have been moved into this proposal . All
the data for this program is acquired using internal targets {lamps}
only, so all of the exposures should be taken during Earth occultation
time {but not during SAA passages}. This program emulates the ACS
pre-flight ground calibration and post-launch SMOV testing {program
8948}, so that results from each epoch can be directly compared.
Extended Pixel Edge Response {EPER} and First Pixel Response {FPR}
data will be obtained over a range of signal levels for both the Wide
Field Channel {WFC}, and the High Resolution Channel {HRC}.

ACS/SBC 10554

Globular Cluster Systems of Elliptical Galaxies in Low Density
Environments

We propose to use the ACS/WFC to determine colour {metallicity}
distributions and luminosity functions for the globular cluster
populations in a well-defined sample of elliptical galaxies in low-
density environments, and to compare the results with similar samples
taken from a rich cluster environment. Low-luminosity ellipticals are
now recognized to play a pivotal role in testing hierarchical models
of galaxy formation, and their globular cluster populations provide a
unique probe of their star formation and metal enrichment history. The
data will be used to {i} determine whether the bimodal colour
distributions indicative of multiple formation epochs in luminous
ellipticals are also prevalent in low-luminosity field ellipticals;
{ii} place joint constraints on age and metallicity in systems with
more than one population and determine the spread of ages in any one
system; {iii} test whether cluster destruction processes {e.g. tidal
shocking} are more effective in low-luminosity ellipticals, as
predicted from their higher mass densities. ACS observations are
essential to eliminate foreground/background contamination and to
probe deep into the luminosity function to obtain a good statistical
sample of clusters. The TAC has previously awarded HST time to two
large surveys of globular cluster systems in rich cluster
environments, but there is currently no comparable survey in
low-density environments with which to compare these results.

ACS/WFC 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with
Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful
"dust free" Type Ia supernovae {SNe Ia} dataset than available with
the previous GOODS searches. Moreover, this approach provides a
strikingly more efficient search-and-follow-up that is primarily pre-
scheduled. The resulting dark energy measurements do not share the
major systematic uncertainty at these redshifts, that of the
extinction correction with a prior. By targeting massive galaxy
clusters at z 1 we obtain a five-times higher efficiency in
detection of Type Ia supernovae in ellipticals, providing a
well-understood host galaxy environment. These same deep cluster
images then also yield fundamental calibrations required for future
weak lensing and Sunyaev-Zel'dovich measurements of dark energy, as
well as an entire program of cluster studies. The data will make
possible a factor of two improvement on supernova constraints on dark
energy time variation, and much larger improvement in systematic
uncertainty. They will provide both a cluster dataset and a SN Ia
dataset that will be a longstanding scientific resource.

ACS/WFC 10503

The Star Formation Histories of Early Type Dwarf Galaxies in Low
Density Environments: Clues from the Sculptor Group

We seek HST ACS/WFC time to conduct a detailed study of the stellar
populations of 5 early-type {dE, dE/dIrr} dwarf galaxies in the nearby
{~1.5 to 4 Mpc} Sculptor group. Four of these systems have been
recently found to contain modest amounts of HI, and existing
ground-based and HST snapshot data point to the potential presence of
small populations of young {blue} stars in at least three of these
systems. Consequently, they resemble the Local Group 'transition'
objects Phoenix and LGS3. The relative number of such transition
systems is thus substantially larger in the low density environment of
the Scl group than for the Local Group. Detailed stellar populations
studies will allow estimation of the star formation histories, via
stellar population modelling of the color-magnitude diagrams, of the
target dwarfs, which in turn will connect to gas consumption and
retention rates. For the two nearer dwarfs we aim to reach below the
horizontal branch {a first for any system beyond the Local Group}
equivalent to a main sequence turnoff age of ~1 Gyr. The observations
of these two systems will also allow detection of RR Lyrae variables
and thus direct confirmation of the presence of old populations. For
the other three dwarfs will we cover the first 2.5 mags of the red
giant branch, equivalent to the main sequence termination for a ~300
Myr population. The results will have implications for theories of
galaxy formation and evolution, particularly with regard to the
evolutionary relation between low luminosity dEs and dwarf irregulars.

ACS/WFC 10635

Galaxy Transformation as probed by Morphology and Velocity Fields of
Distant Cluster Galaxies

We seek to obtain ACS imaging of four distant {0.3z0.6} clusters of
galaxies within a 6'x6' field covered by a 2x2 mosaic to determine
morphological and structural parameters of late-type galaxies. We
specifically concentrate on peculiarities indicative of past or
ongoing interaction processes. The ~90 target galaxies have been
{Period74} or will be {P75} observed with 3D- spectroscopy at ESO-VLT
yielding 2D-velocity fields with unprecedented spatial coverage and
sampling. The good spatial resolution of the ground-based data will be
further enhanced by a deconvolution method based on the proposed ACS
images. The velocity field and the morphology in restframe-UV light
will reveal possible transformation mechanisms affecting not only the
stellar populations but also the mass distribution of the galaxies.
Additionally, it will be possible to pin down the nature of the
interaction {e.g. tidally or ram-pressure induced}. This assessment
gets supported by our N-body/SPH simulations {including star
formation} of different interaction processes that allow the direct
comparison of structural and kinematical characteristics at each time
step with the observations on an individual basis taking into account
all observational constraints for a given galaxy. All together, we
will be able to explore the relative efficiency of the various
proposed transformation phenomena. In the case of non-disturbed
spirals, a rotation curve can be extracted from the full 2D velocity
field with unprecedented quality, from which the maximum rotation
speed can be derived with high confidence. In combination with
accurate size and luminosity determinations from the ACS images, we
will be able to establish the Tully-Fisher and Fundamental Plane
relations of cluster spiral members at cosmological epochs. At these
distances cluster assembly is predicted to peak and we can probe the
galaxies' luminosity, size and mass evolution with robust methods.
Together with our already existing sample of ~200 distant {z=1}
spiral galaxies in the field, we will put strong constraints on
current theories of galaxy formation and evolution in different
environments.

FGS 10612

Binary Stars in Cyg OB2: Relics of Massive Star Formation in a
Super-Star Cluster

We propose to make a high angular resolution SNAP survey of the
massive stars in the nearby, super-star cluster Cyg OB2. We will use
FGS1r TRANS mode observations to search for astrometric companions in
the separation range of 0.01 to 1.00 arcsec and in the magnitude
difference range smaller than 4 magnitudes. The observations will test
the idea that the formation of very massive stars involves mergers and
the presence of nearby companions. Discovery of companions to massive
stars in this relatively nearby complex will provide guidance in the
interpretation of apparently supermassive stars in distant locations.
The search for companions will also be important for verification of
fundamental parameters derived from spectroscopy, adjustments to main
sequence fitting and distance estimations, determining third light
contributions of eclipsing binaries, identifying wide colliding wind
binaries, studying the relationship between orbital and spin angular
momentum, and discovering binaries amenable to future mass
determinations. The massive star environment in Cyg OB2 may be similar
to the kinds found in the earliest epoch of star formation, so that a
study of the role of binaries in Cyg OB2 will help us understand the
formation processes of the first stars in the Universe.

WFPC2 10745

WFPC2 CYCLE 14 INTERNAL MONITOR

This calibration proposal is the Cycle 14 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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10264 - FGS1 requires multiple attempts to achieve CT-DV @ 130/0710z
OTA SE processing of PTAS data revealed that FGS1 required multiple
attempts to achieve CT-DV during GSAcq(1,2,2) scheduled for
130/07:10:43.

10265 - FGS2 requires multiple attempts to achieve CT-DV @ 132/0528z
OTA SE processing of PTAS data revealed that FGS2 required multiple
attempts to achieve CT-DV during ReAcq(2,3,3) scheduled for
132/05:28:31.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 11 11
FGS
REacq 04 04

OBAD with Maneuver 30 30

SIGNIFICANT EVENTS:

Subject : SMS SA135Q04: distribution of final products

THIS IS AN INTERCEPT SMS
This SMS includes three target of opportunity visits from
program 10551.

Intercept time: 2006.137:19:44:47
First command difference:2006.139:02:49:04
First Uplink Time: 2006.137:07:58:51

SMS SA135Q04 was authorized @ 137/0050z