Daily Report #4390

Notice: For the foreseeable future, the daily reports may contain apparent
discrepancies between some proposal descriptions and the listed instrument
usage. This is due to the conversion of previously approved ACS WFC or HRC
observations into WFPC2, or NICMOS observations subsequent to the loss of
ACS CCD science capability in late January.


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4390

PERIOD COVERED: UT June 22,23,24, 2007 (DOY 173,174,175)

OBSERVATIONS SCHEDULED

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 11157

NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar
Mass Spectrum

Association of planetary systems with dusty debris disks is now quite
secure, and advances in our understanding of planet formation and evolution
can be achieved by the identification and characterization of an ensemble of
debris disks orbiting a range of central stars with different masses and
ages. Imaging debris disks in starlight scattered by dust grains remains
technically challenging so that only about a dozen systems have thus far
been imaged. A further advance in this field needs an increased number of
imaged debris disks. However, the technical challege of such observations,
even with the superb combination of HST and NICMOS, requires the best
targets. Recent HST imaging investigations of debris disks were
sample-limited not limited by the technology used. We performed a search for
debris disks from a IRAS/Hipparcos cross correlation which involved an
exhaustive background contamination check to weed out false excess stars.
Out of ~140 identified debris disks, we selected 22 best targets in terms of
dust optical depth and disk angular size. Our target sample represents the
best currently available target set in terms of both disk brightness and
resolvability. For example, our targets have higher dust optical depth, in
general, than newly identified Spitzer disks. Also, our targets cover a
wider range of central star ages and masses than previous debris disk
surveys. This will help us to investigate planetary system formation and
evolution across the stellar mass spectrum. The technical feasibility of
this program in two-gyro mode guiding has been proven with on- orbit
calibration and science observations during HST cycles 13, 14, and 15.

WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group: Complementing
the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming regions
in the Local Group galaxies, to resolve their young stellar populations. We
will use a set of filters including F170W, which is critical to detect and
characterize the most massive stars, to whose hot temperatures colors at
longer wavelengths are not sensitive. WFPC2's field of view ideally matches
the typical size of the star-forming regions, and its spatial resolution
allows us to measure indvidual stars, given the proximity of these galaxies.
The resulting H- R diagrams will enable studies of star-formation properties
in these regions, which cover largely differing metallicities {a factor of
17, compared to the factor of 4 explored so far} and characteristics. The
results will further our understanding of the star-formation process, of the
interplay between massive stars and environment, the properties of dust, and
will provide the key to interpret integrated measurements of star-formation
indicators {UV, IR, Halpha} available for several hundreds more distant
galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV}
and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the
identification of the most relevant SF sites. In addition to our scientific
analysis, we will provide catalogs of HST photometry in 6 bands, matched
corollary ground-based data, and UV, Halpha and IR integrated measurements
of the associations, for comparison of integrated star-formation indices to
the resolved populations. We envisage an EPO component.

WFPC2 11040

Geometric Distortion / Astrometry Closeout

These observations will serve as a final characterization of the geometric
distortion and astrometric calibration. The Omega-Cen inner calibration
field is used. Filters F300W, F555W, and F814W are observed at 5 roll angles
spanning 180 degrees; F218W is observed at a single roll angle.

FGS 11019

Monitoring FGS1r's Interferometric Response as a Function of Spectral Color

This proosal uses FGS1r in Transfer mode to observe standard single stars of
a variety of spectral types to obtain point source interferograms for the
Transfer mode calibration library. In specific cases, the calibration star
will also be observed in POS mode multiple times with the F583W and F5ND
elements to provide the data to verify the stabiligy of the cross filter
calibration.

WFPC2 10922

Searching for Signs of a Double Generation of Stars in Galactic Globular
Clusters

This proposal has been stimulated by new findings of ours that may have a
strong impact on the interpretation of globular cluster {GC} stellar
populations. In 2004, based on HST data, we have found that the main
sequence of the Galactic globular cluster Omega Centauri is split into two
sequences; spectroscopic analysis has shown that the only isochrones which
are able to fit the combination of color and metallicity of the bluest of
the two sequences were younger and greatly enriched in helium. A number of
observational facts, and theoretical evidence suggest that our results on
Omega Centauri might represent an extreme case of a phenomenon which has
also been at work in other GCs. We have selected the most promising GCs to
find out whether this hypothesis is correct, and make a strong case for its
likelihood and the value of pursuing it.

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 tha 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 10890

Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies

The formative phase of the most massive galaxies may be extremely luminous,
characterized by intense star- and AGN-formation. Till now, few such
galaxies have been unambiguously identified at high redshift, restricting us
to the study of low-redshift ultraluminous infrared galaxies as possible
analogs. We have recently discovered a sample of objects which may indeed
represent this early phase in galaxy formation, and are undertaking an
extensive multiwavelength study of this population. These objects are bright
at mid-IR wavelengths {F[24um]0.8mJy}, but deep ground based imaging
suggests extremely faint {and in some cases extended} optical counterparts
{R~24-27}. Deep K-band images show barely resolved galaxies. Mid-infrared
spectroscopy with Spitzer/IRS reveals that they have redshifts z ~ 2-2.5,
suggesting bolometric luminosities ~10^{13-14}Lsun! We propose to obtain
deep ACS F814W and NIC2 F160W images of these sources and their environs in
order to determine kpc-scale morphologies and surface photometry for these
galaxies. The proposed observations will help us determine whether these
extreme objects are merging systems, massive obscured starbursts {with
obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted
by intrinsically low-luminosity galaxies.

WFPC2 10877

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for
supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS},
have found hundreds of SNe, many of them in quite nearby galaxies {cz 4000
km/s}. Most of the objects were discovered before maximum brightness, and
have follow-up photometry and spectroscopy; they include some of the
best-studied SNe to date. We propose to conduct a snapshot imaging survey of
the sites of some of these nearby objects, to obtain late-time photometry
that {through the shape of the light and color curves} will help reveal the
origin of their lingering energy. The images will also provide
high-resolution information on the local environments of SNe that are far
superior to what we can procure from the ground. For example, we will obtain
color-color and color-magnitude diagrams of stars in these SN sites, to
determine the SN progenitor masses and constraints on the reddening.
Recovery of the SNe in the new HST images will also allow us to actually
pinpoint their progenitor stars in cases where pre- explosion images exist
in the HST archive. This proposal is an extension of our successful Cycle 13
snapshot survey with ACS. It is complementary to our Cycle 15 archival
proposal, which is a continuation of our long-standing program to use
existing HST images to glean information about SN environments.

ACS/SBC 10872

Lyman Continuum Emission in Galaxies at z=1.2

Lyman continuum photons produced in massive starbursts may have played a
dominant role in the reionization of the Universe. Starbursts are important
contributors to the ionizing metagalactic background at lower redshifts as
well. However, their contribution to the background depends upon the
fraction of ionizing radiation that escapes from the intrinsic opacity of
galaxies below the Lyman limit. Current surveys suggest escape fractions of
a few percent, up to 10%, with very few detections {as opposed to upper
limits} having been reported. No detections have been reported in the epochs
between z=0.1 and z=2. We propose to measure the fraction of escaping Lyman
continuum radiation from 15 luminous z~1.2 galaxies in the GOODS fields.
Using the tremendous sensitivity of the ACS Solar- blind Channel, we will
reach AB=30 mag., allowing us to detect an escape fraction of 1%. We will
correlate the amount of escaping radiation with the photometric and
morphological properties of the galaxies. A non-detection in all sources
would imply that QSOs provide the overwhelming majority of ionizing
radiation at z=1.3, and it would strongly indicate that the properties of
galaxies at higher redshift have to be significantly different for galaxies
to dominate reionization. The deep FUV images will also be useful for
extending the FUV study of other galaxies in the GOODS fields.

NIC2 10849

Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space
Telescope around 21 Sun-like Stars

We propose to use the high-contrast capability of the NICMOS coronagraph to
image a sample of newly discovered circumstellar disks associated with
Sun-like stars. These systems were identified by their strong thermal
infrared {IR} emission with the Spitzer Space Telescope as part of the
Spitzer Legacy Science program titled "The Formation and Evolution of
Planetary Systems" {FEPS, P.I.: M.Meyer}. Modeling of the thermal excess
emission from the spectral energy distributions alone cannot distinguish
between narrowly confined high-opacity disks and broadly distributed,
low-opacity disks. By resolving light scattered by the circumstellar
material, our proposed NICMOS observations can break this degeneracy, thus
revealing the conditions under which planet formation processes are occuring
or have occured. For three of our IR-excess stars that have known
radial-velocity planets, resolved imaging of the circumstellar debris disks
may further offer an unprecedented view of planet-disk interactions in an
extrasolar planetary system. Even non-detections of the light scattered by
the circumstellar material will place strong constraints on the disk
geometries, ruling out disk models with high optical depth. Unlike previous
disk imaging programs, our program contains a well-defined sample of ~1
solar mass stars covering a range of ages from 3 Myr to 3 Gyr, thus allowing
us to study the evolution of disks from primordial to debris for the first
time. The results from our program will greatly improve our understanding of
the architecture of debris disks around Sun-like stars, and will create a
morphological context for the existence of our own solar system. This
proposal is for a continuation of an approved Cycle 14 program {GO/10527,
P.I.: D. Hines}.

WFPC2 10834

The Shell of the Recurrent Nova T Pyx

T Pyx is the only known recurrent nova with a shell. This 'shell' is
mysterious because it has been resolved into thousands of knots that
apparently aren't expanding. We propose to take a deep F658N image of T Pyx
during one orbit to serve as a 12 year baseline from the previous HST WFPC2
images in 1994 and 1995. This much longer baseline will allow us to push
down the limits on expansion velocities to ~10 km/s and will allow us to
measure the lifetimes of the knots. Also, we expect to discover the
expanding inner shell from the last eruption in 1966 which should now have
expanded to ~0.9" in radius. Detailed modeling of the observed line fluxes
will give the mass of the individual knots and the shells. The details of
the expansion velocities, lifetimes, and masses of the knots will determine
the nature of the T Pyx shell; with alternatives being a nova shell, a
planetary nebula, stalled shocks in a pre-existing shell, or a cloud ionized
by the high luminosity and temperature of the white dwarf. If we can
separate out the mass ejected during the 1966 eruption, then we can compare
it to the total mass accreted between the 1944 and 1966 eruptions {6.0x10^-6
solar mass} so as to determine whether the white dwarf is gaining or losing
mass on average. If the white dwarf is gaining mass, then it must inevitably
exceed the Chandrasekhar mass and collapse as a Type Ia supernova, and thus
recurrent novae would be shown to be an important component of the solution
to the Type Ia progenitor problem.

ACS/SBC 10810

The Gas Dissipation Timescale: Constraining Models of Planet Formation

We propose to constrain planet-formation models by searching for molecular
hydrogen emission around young {10-50 Myr} solar-type stars that have
evidence for evolved dust disks. Planet formation models show that the
presence of gas in disks is crucial to the formation of BOTH giant and
terrestrial planets, influences dust dynamics, and through tidal
interactions with giant planets leads to orbital migration. However, there
is a lack of systematic information on the presence and lifetime of gas
residing at planet-forming radii. We will use a newly identified broad
continuum emission feature of molecular hydrogen at 1600 Angstrom to search
for residual gas within an orbital radius of 5-10 AU around young stars that
have evolved beyond the optically thick T Tauri phase. These observations
will enable the most sensitive probe to date of remant gas in circumstellar
disks, detecting surfaces densites of ~0.0001 g/cm^2, or less than 10^-5 of
the theoretical "mininum mass" solar nebula from which our solar system is
thought to have formed. Our observations are designed to be synergistic with
ongoing searches for gas emission that is being performed using the Spitzer
Space Telescope in that the proposed HST observations are ~100 times more
sensitive and will have 50 times higher angular resolution. These combined
studies will provide the most comprehensive view of residual gas in
proto-planetary disks and can set important constraints on models of planet
formation.

WFPC2 10807

The knotty jet of He 2-90: An ideal laboratory for studying the formation
and propagation of jets in dying stars

Previous WFPC2 observations have led to the serendipitous discovery of an
extended, highly-collimated, ``pulsed" bipolar jet emanating from a compact
planetary nebula, He 2- 90. Subsequently, an average proper motion of the
knots in the jet was measured, which together with radial velocities,
enabled us to characterise the basic physical properties of the jet. The
knotty jet in He 2-90 resembles other prominent examples of pulsed jets in
young stellar objects or symbiotic stars, but is probably by far the best
example yet of a non-relativistic, symmetric, jet in a ``clean"
astrophysical environment. The formation {acceleration and collimation} of
jets is not fully understood, specially in the case of jets in dying stars.
We now propose to re-image He 2-90 with WFPC2 and exploit the factor 3.5
longer time baseline now available from the first-epoch observations in
September 1999, in order to measure the proper motion of individual knots in
the jet with unprecedented accuracy. These data will enable us to
characterise the ejection history of the source, specially deviations from a
constant period {latter is related to the binary period of the system},
e.g., due to instabilities in the accretion mechanism. We will also be able
to test if the ejection mechanism is symmetric: any deviation in the
ejection history of the knots in the opposing jet beams, will indicate a
magnetic field structure and/or the accretion disk which is not symmetric
across the equatorial plane. We will also carry out deep imaging with the
ACS/WFC camera in order to determine the shapes/sizes of a large number of
knots. The shapes/sizes of the knots, and changes with distance from the
source probe the strength of the magnetic field inside the jet. HRC imaging
of the central source and jet on sub-arcsecond scales will be carried out to
probe the magnetic field close to the jet source, and deviations from
linearity in the jet-beam which may result from instabilities in the
magnetic field. These data will allow us to significantly improve our
existing 2- dimensional MHD model of the He2-90 jet, and/or provide impetus
for new 3-dimensional models.

WFPC2 10800

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the early
dynamical evolution of the outer Solar System. We propose to continue a
Snapshot program using the ACS/HRC that has a demonstrated discovery
potential an order of magnitude higher than the HST observations that have
already discovered the majority of known transneptunian binaries. With this
continuation we seek to reach the original goals of this project: to
accumulate a sufficiently large sample in each of the distinct populations
collected in the Kuiper Belt to be able to measure, with statistical
significance, how the fraction of binaries varies as a function of their
particular dynamical paths into the Kuiper Belt. Today's Kuiper Belt bears
the imprints of the final stages of giant-planet building and migration;
binaries may offer some of the best preserved evidence of that long-ago era.

NIC3 10504

Characterizing the Sources Responsible for Cosmic Reionization

Our group has demonstrated the role that massive clusters, acting as
powerful cosmic lenses, can play in constraining the abundance and
properties of low-luminosity star- forming sources beyond z~6; such sources
are thought to be responsible for ending cosmic reionization. The large
magnification possible in the critical regions of well- constrained clusters
brings sources into view that lie at or beyond the limits of conventional
exposures such as the UDF, as well as those in imaging surveys being
undertaken with IRAC onboard Spitzer. We have shown that the combination of
HST and Spitzer is particularly effective in delivering the physical
properties of these distant sources, constraining their mass, age and past
star formation history. Indirectly, we therefore gain a valuable glimpse to
yet earlier epochs. Recognizing the result {and limitations} of the UDF
exposure, we propose a systematic search through 6 lensing clusters with ACS
and NICMOS for further z~6-7 sources in conjunction with existing deep IRAC
data. Our survey will mitigate cosmic variance and extend the search both to
lower luminosities and, by virtue of the NICMOS/IRAC combination, to higher
redshift. The goal is to count and characterize representative sources at
z~6-10 and to delineate the redshift range of activity for the planning of
future observations.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10868 - GSAcq(1,2,1) failed to RGA Hold (Gyro Control)

Upon acquisition of signal at 174/06:56:20, the GSAcq(1,2,1) scheduled at
174/05:39:58 - 05:48:03 had failed to RGA Hold due to (QF1STOPF) stop flag
indication on FGS-1. Pre-acquisition OBADs (RSS) attitude correction values
not available. Post-acq OBAD/MAP had (RSS) value of 812.49 arcseconds.

10869 - GSAcq(1,2,1) failed to RGA Hold (Gyro Control)

Upon acquisition of signal (AOS) at 175/06:06:35, the GSAcq(1,2,1) scheduled
at 175/05:38:12 - 05:46:17 had failed to RGA Hold due to (QF1STOPF) stop
flag indication on FGS-1. Pre-acquisition OBAD1 attitude correction value
not available due to LOS. OBAD2 had (RSS) value of 8.95 arcseconds. Post-acq
OBAD/MAP had (RSS) value of 929.22 arcseconds.

COMPLETED OPS REQUEST:

18110-0 - Configure Kalman Filter for MSS/CSS/Gyro2 monitoring

SCHEDULED SUCCESSFUL

FGS GSacq 19 17
FGS REacq 18 18
OBAD with Maneuver 74 74

COMPLETED OPS NOTES: (None)

SIGNIFICANT EVENTS:

Flash Report: Background Kalman Filter Operation.

The Kalman Filter was reconfigured to an MSS/CSS/Gyro2 configuration at
173/18:22 in support of a long-term KF monitoring test. It will remain in
this configuration for approximately a week.