Daily Rpt #4405

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 # 4405

PERIOD COVERED: UT July 16, 2007 (DOY 197)

OBSERVATIONS SCHEDULED

ACS/WFC/WFPC2 10904

Star formation in extended UV disk {XUV-disk} galaxies

The Galaxy Evolution Explorer {GALEX} has discovered the existence of
extended UV-disk {XUV-disk} galaxies. This class of intriguing spiral
galaxies is distinguished by UV-bright regions of star formation located at
extreme galactocentric radii, commonly reaching many times the optical
extent of each target. XUV-disks represent a population of late-type
galaxies still actively building, or significantly augmenting, their stellar
disk in the outer, low-density environment. Prior to GALEX, such regions
were considered to be far more stable against star formation than now
realized. Our work on these targets has led to the recognition of the XUV
phenomenon as probing a diverse population of galaxies which, although
having certain commonality in terms of their present XUV star formation,
have apparently experienced different star formation histories {as judged by
their outer disk UV-optical colors and morphology}. In ordinary spirals,
disk formation occurred at a much earlier epoch, making today's XUV-disks
useful templates for commonplace, high z galaxies. The diverse XUV-disks in
our sample may represent snapshots of different phases in the disk building
process. We seek to characterize the demographics of star forming regions
occupying this environmental range, especially in contrast to their inner
disk counterparts. HST imaging is needed to accurately characterize the
massive stars and clusters which have, in fact, managed to form. The GALEX
observations are limited by 5" resolution. Deep ACS FUV, B, V, I, and
H-alpha imaging {along with parallel WFPC2 data} will allow: {1} photometric
classification of the OB star population, {2} constraint on the cluster mass
function and age distribution, {3} critical accounting for possible leakage
of Lyman continuum photons in a porous ISM or an IMF change, and {4}
population synthesis modeling of the field SFH on Gyr timescales. We benefit
from extensive archival HST observations of our target galaxies, although
the outer disk has yet to be probed.

FGS 11210

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that
prediction. It is, however, a prediction of extrasolar planetary system
architecture as yet untested by direct observation for main sequence stars
other than the Sun. To provide such a test, we propose to carry out FGS
astrometric studies on four stars hosting seven companions. Our
understanding of the planet formation process will grow as we match not only
system architecture, but formed planet mass and true distance from the
primary with host star characteristics for a wide variety of host stars and
exoplanet masses. We propose that a series of FGS astrometric observations
with demonstrated 1 millisecond of arc per-observation precision can
establish the degree of coplanarity and component true masses for four
extrasolar systems: HD 202206 {brown dwarf+planet}; HD 128311
{planet+planet}, HD 160691 = mu Arae {planet+planet}, and HD 222404AB =
gamma Cephei {planet+star}. In each case the companion is identified as such
by assuming that the minimum mass is the actual mass. For the last target, a
known stellar binary system, the companion orbit is stable only if coplanar
with the AB binary orbit.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

A new procedure proposed to alleviate the CR-persistence problem of NICMOS.
Dark frames will be obtained immediately upon exiting the SAA contour 23,
and every time a NICMOS exposure is scheduled within 50 minutes of coming
out of the SAA. The darks will be obtained in parallel in all three NICMOS
Cameras. The POST-SAA darks will be non-standard reference files available
to users with a USEAFTER date/time mark. The keyword 'USEAFTER=date/time'
will also be added to the header of each POST-SAA DARK frame. The keyword
must be populated with the time, in addition to the date, because HST
crosses the SAA ~8 times per day so each POST-SAA DARK will need to have the
appropriate time specified, for users to identify the ones they need. Both
the raw and processed images will be archived as POST-SAA DARKSs. Generally
we expect that all NICMOS science/calibration observations started within 50
minutes of leaving an SAA will need such maps to remove the CR persistence
from the science images. Each observation will need its own CRMAP, as
different SAA passages leave different imprints on the NICMOS detectors.

NIC3 10874

Search for Extremely Faint z7 Galaxy Population with Cosmic Lenses

Deep UDF/NICMOS observations find a significant decrease in the number of
galaxy candidates between redshift z=6 and 7, but the sample at z7 is too
small to draw conclusions. From our observations of 15 clusters we have
found a number of bright z-dropouts, aided by the lensing amplification. We
propose deep NICMOS observations of the best cases of cluster centers where
a rare combination of a significant lensing effect and the richness in
z-band dropouts in background may dramatically increase the discovery rate.
The NICMOS images will reach an unprecedented depth of AB~27.8, or AB~30 in
nonlensed intrinsic magnitude, and may find many faint {~0.05L*} galaxies at
z=7-10, at a level that the UDF reaches for z~6 objects. We produce
precision mass distribution maps from weak-lensing models, which enable us
to derive the candidates' intrinsic magnitudes and their luminosity
function. The knowledge of such faint galaxy population at z7 will
facilitate the models of the IGM reionization and future JWST planning.

WFPC2 11022

WFPC2 Cycle 15 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors
tied to decons: photometric stability check, focus monitor, pre- and
post-decon internals {bias, intflats, kspots, & darks}, UV throughput check,
VISFLAT sweep, and internal UV flat check.

WFPC2 11178

Probing Solar System History with Orbits, Masses, and Colors of
Transneptunian Binaries

The recent discovery of numerous transneptunian binaries {TNBs} opens a
window into dynamical conditions in the protoplanetary disk where they
formed as well as the history of subsequent events which sculpted the outer
Solar System and emplaced them onto their present day heliocentric orbits.
To date, at least 47 TNBs have been discovered, but only about a dozen have
had their mutual orbits and separate colors determined, frustrating their
use to investigate numerous important scientific questions. The current
shortage of data especially cripples scientific investigations requiring
statistical comparisons among the ensemble characteristics. We propose to
obtain sufficient astrometry and photometry of 23 TNBs to compute their
mutual orbits and system masses and to determine separate primary and
secondary colors, roughly tripling the sample for which this information is
known, as well as extending it to include systems of two near-equal size
bodies. To make the most efficient possible use of HST, we will use a Monte
Carlo technique to optimally schedule our observations.

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: (None)

COMPLETED OPS REQUEST: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 07 07
FGS REacq 08 08
OBAD with Maneuver 30 30

COMPLETED OPS NOTES: (None)

SIGNIFICANT EVENTS: (None)