Daily Report #4408

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 # 4408

PERIOD COVERED: UT July 19, 2007 (DOY 200)

OBSERVATIONS SCHEDULED

ACS/SBC 10907

New Sightlines for the Study of Intergalactic Helium: A Dozen
High-Confidence, UV-Bright Quasars from SDSS/GALEX

The reionization of intergalactic helium is thought to have occurred
between redshifts of about 3 and 4. Detailed study of HeII Lyman-alpha
absorption toward a handful quasars at 2.7z3.3 demonstrates the
great potential of such probes of the IGM, but the current
critically-small sample limits confidence in resulting cosmological
inferences. The requisite unobscured quasar sightlines to
high-redshift are extremely rare, especially due to severe absorption
in random intervening Lyman-limit systems, but SDSS provides thousands
of z3.1 quasars potentially suitable for HeII studies. We have
cross-correlated SDSS quasars with GALEX UV sources to obtain a dozen
new, very high-confidence, candidate quasars/sightlines {z=3.1 to 4.1}
potentially useful for detailed HeII studies even with current HST
instruments. We propose brief, 2-orbit per target, reconnaissance
spectral exposures with the ACS SBC prism to definitively verify UV
flux down to the HeII break. Our combined SDSS/GALEX selection insures
a very high- yield of confirmations, as the quasars are already known
to be UV-bright from broadband GALEX images. The additional
sightlines, extending to very high-redshift, will directly enable
ensemble spectral stacks, as well as long exposure follow-up spectra,
at high S/N with the ACS/SBC ultraviolet prisms {or perhaps STIS or
COS later}, to confidently measure the spectrum and evolution of the
ionizing background radiation, the evolution of HeII opacity, and the
density of intergalactic baryons.

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.

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.

NIC2 10893

Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble
Diagram

We propose building a high-z Hubble Diagram using type Ia supernovae
observed in the infrared rest-frame J-band. The infrared has a number
of exceptional properties. The effect of dust extinction is minimal,
reducing a major systematic that may be biasing dark energy
measurements. Also, recent work indicates that type Ia supernovae are
true standard candles in the infrared meaning that our Hubble diagram
will be resistant to possible evolution in the Phillips relation over
cosmic time. High signal-to-noise measurements of 9 type Ia events at
z~0.4 will be compared with an independent optical Hubble diagram from
the ESSENCE project to test for a shift in the derived dark energy
equation of state due to a systematic bias. Because of the bright sky
background, H-band photometry of z~0.4 supernovae is not feasible from
the ground. Only the superb image quality and dark infrared sky seen
by HST makes this test possible. This experiment may also lead to a
better, more reliable way of mapping the expansion history of the
universe with the Joint Dark Energy Mission.

WFPC2 10818

Very Young Globular Clusters in M31 ?

We propose to use HST's unique high spatial resolution imaging
capabilities to conclusively confirm or refute the presence of alleged
very young globular clusters in M31. Such young globular clusters with
ages 3 Gyr are not present in our galaxy, and, if real, would lead
to a striking difference in the age distribution of the GCs between
M31 and the Millky Way. If the apparent presence of very young
globular clusters in M31 is confirmed through our proposed ACS imaging
{now WFPC2 imaging} with HST, this would suggest major differences in
the history of assembly of the two galaxies, with probable substantial
late accretion into M31 which did not occur in our own galaxy.

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 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still
largely an open problem in cosmology: how does the Universe evolve
from large linear scales dominated by dark matter to the highly
non-linear scales of galaxies, where baryons and dark matter both play
important, interacting, roles? To understand the complex physical
processes involved in their formation scenario, and why they have the
tight scaling relations that we observe today {e.g. the Fundamental
Plane}, it is critically important not only to understand their
stellar structure, but also their dark-matter distribution from the
smallest to the largest scales. Over the last three years the SLACS
collaboration has developed a toolbox to tackle these issues in a
unique and encompassing way by combining new non-parametric strong
lensing techniques, stellar dynamics, and most recently weak
gravitational lensing, with high-quality Hubble Space Telescope
imaging and VLT/Keck spectroscopic data of early-type lens systems.
This allows us to break degeneracies that are inherent to each of
these techniques separately and probe the mass structure of early-type
galaxies from 0.1 to 100 effective radii. The large dynamic range to
which lensing is sensitive allows us both to probe the clumpy
substructure of these galaxies, as well as their low-density outer
haloes. These methods have convincingly been demonstrated, by our
team, using smaller pilot-samples of SLACS lens systems with HST data.
In this proposal, we request observing time with WFPC2 and NICMOS to
observe 53 strong lens systems from SLACS, to obtain complete
multi-color imaging for each system. This would bring the total number
of SLACS lens systems to 87 with completed HST imaging and effectively
doubles the known number of galaxy-scale strong lenses. The deep HST
images enable us to fully exploit our new techniques, beat down
low-number statistics, and probe the structure and evolution of early-
type galaxies, not only with a uniform data-set an order of magnitude
larger than what is available now, but also with a fully coherent and
self-consistent methodological approach!

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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

#10901 MNDRDT1 & MNDRDT2 out of limits for 1 minute.

At 200/15:03:03 the mnemonics MNDRDT1 & MNDRDT2 (NCS CPL RES-RAD B
DELTA T) flagged out of limits - red low at 5.3725 & 6.46859
respectively. They returned back in bounds at 200/15:04:02. the red
lower limit is set at 7.0.

#10902 OBAD Failed Identification (ESB 1902), GSAcq not attempted.

At 200/15:33:26z "OBAD failed". The second OBAD failed during LOS
scheduled 15:33:38-15;46;00z. Other data included: Mnemonic GOBSTAT =
255, GCHACL09 = 1, TGS Mode = T2G.

GSAcq (1,3,1) scheduled from 15:43:55-15:50:59 was not attempted.
OBAD #1: V1 5.77, V2 -3.06, V3 -9.55, RSS 11.57
OBAD #2: V1 -33466.27, V2 -13497.54, V3 24133.27, RSS 43411.86
OBAD MAP: V1 -131.31, V2 131.93, V3 -105.57, RSS 213.99

REAcq (1,3,1) scheduled for 17:21:35-17:28:56 failed. No data
available due to LOS.

#10903 GSACQ(1,3,1) failed.

GSACQ(1,3,1) at 200/20:36:06 failed to RGA control. No FGS flags were
seen. Vehicle was LOS at time of failure. At acquisition of signal
vehicle had OBAD RSS error of 11020.84 arcseconds.

COMPLETED OPS REQUEST: (None)

******************************* SCHEDULED* SUCCESSFUL

FGS GSacq********************** 08************** 06
FGS REacq********************** 07************** 06
OBAD with Maneuver******* ***** 30*************** 27

COMPLETED OPS NOTES: (None)

SIGNIFICANT EVENTS: (None)