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.