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      # 4350

PERIOD COVERED: UT April 26, 2007 (DOY 116)

OBSERVATIONS SCHEDULED

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.

WFPC2 10803

Detecting the progenitors of core-collapse supernovae

Modern supernova searches in the nearby Universe are discovering large

numbers of SNe which have massive star progenitors {Types II, Ib and

Ic}. The extensive HST image archive within ~20Mpc enables the indvidual

bright stellar content of starforming galaxies to be resolved. As

massive, evolved stars are the most luminous single objects in a galaxy,

the progenitors of core-collapse SNe are often directly detectable on

pre-explosion archive images. We have discovered three progenitors of

recent type II-Plateau SNe, showing them to be red supergiants of 8-12

solar masses. This is the first direct evidence that red supergiants do

indeed produce normal type II explosions. We have set upper mass limits

on a further 7 progenitor stars and suggest that faint type II

supernovae are unlikely to come from the collapse of very massive stars

which form black holes. These discoveries are providing strong

constraints on theoretical models of pre-supernova evolution, explosion

models and the origin of the supernova types. We request time to

continue this successful project and require ACS observations of future

SNe which are discovered in galaxies closer than 20Mpc and which have

pre-explosion HST archive images available. This will allow the SNe to

be precisely positioned on the pre-explosion images. We have set a final

goal for this project of determining masses and types, or setting

restrictive mass-limits, for 30 supernovae over the remainder of HST's

project life.

WFPC2 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey

for new strong gravitational lenses, we propose one orbit of ACS-WFC

F814W imaging for each of 50 high-probability strong galaxy-galaxy lens

candidates. These observations will confirm new lens systems and permit

immediate and accurate photometry, shape measurement, and mass modeling

of the lens galaxies. The lenses delivered by the SLACS Survey all show

extended source structure, furnishing more constraints on the projected

lens potential than lensed-quasar image positions. In addition, SLACS

lenses have lens galaxies that are much brighter than their lensed

sources, facilitating detailed photometric and dynamical observation of

the former. When confirmed lenses from this proposal are combined with

lenses discovered by SLACS in Cycles 13 and 14, we expect the final

SLACS lens sample to number 80--100: an approximate doubling of the

number of known galaxy-scale strong gravitational lenses and an

order-of-magnitude increase in the number of optical Einstein rings. By

virtue of its homogeneous selection and sheer size, the SLACS sample

will allow an unprecedented exploration of the mass structure of the

early-type galaxy population as a function of all other observable

quantities. This new sample will be a valuable resource to the

astronomical community by enabling qualitatively new strong lensing

science, and as such we will waive all but a short {3-month} proprietary

period on the observations.

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.

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 11032

CTE Extended Targets Closeout

Measuring the charge transfer efficiency {CTE} of an astronomical CCD

camera is crucial to determining the CCD's photometric fidelity across

the field of view. WFPC2's CTE has degraded steadily over the last 13

years because of continuous exposure to trapped particles in HST's

radiation environment. The fraction of photometric signal lost from

WFPC2's CTI {change transfer inefficiency} is a function of WFPC2's time

in orbit, the integrated signal in the image, the location of the image

on the CCD, and the background signal. Routine monitoring of WFPC2's

degrading CTE over the last 13 years has primarily concerned the effects

of CTI on point-source photometry. However, most of the sources imaged

by WFPC2 are extended rather than point-like. This program aims to

characterize the effects of CTI on the photometry and morphology of

extended sources near the end of WFPC2's functional life. Images of a

standard field within the rich galaxy cluster Abell 1689 are recorded

with each WFPC2 camera using the F606W and F814W filters. These images

will be compared with contemporaneous images of Abell 1689 recorded with

the field rotated by approximately 180 degrees to assess differences

between extended sources imaged near and far from the serial register.

The images will also be compared with similar images recorded in Cycle 8

{Program 8456} to characterize the rate of CTE degradation over the

lifetime of WFPC2.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey

{ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased

sample of 100 early-type galaxies in the Virgo Cluster. On subarcsecond

scales {i.e., <0.1"-1"}, the HST brightness profiles vary systematically

from the brightest giants {which have nearly constant surface brightness

cores} to the faintest dwarfs {which have compact stellar nuclei}.

Remarkably, the fraction of galaxy mass contributed by the nuclei in the

faint galaxies is identical to that contributed by supermassive black

holes in the bright galaxies {0.2%}. These findings strongly suggest

that a single mechanism is responsible for both types of Central Massive

Object: most likely internally or externally modulated gas inflows that

feed central black holes or lead to the formation of "nuclear star

clusters". Understanding the history of gas accretion, star formation

and chemical enrichment on subarcsecond scales has thus emerged as the

single most pressing question in the study of nearby galactic nuclei,

either active or quiescent. We propose an ambitious HST program {199

orbits} that constitutes the next, obvious step forward:

high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W}

imaging for the complete ACSVCS sample. By capitalizing on HST's unique

ability to provide high-resolution images with a sharp and stable PSF at

UV and IR wavelengths, we will leverage the existing optical HST data to

obtain the most complete picture currently possible for the history of

star formation and chemical enrichment on these small scales. Equally

important, this program will lead to a significant improvement in the

measured structural parameters and density distributions for the stellar

nuclei and the underlying galaxies, and provide a sensitive measure of

"frosting" by young stars in the galaxy cores. By virtue of its superb

image quality and stable PSF, NICMOS is the sole instrument capable of

the IR observations proposed here. In the case of the WFPC2

observations, high-resolution UV imaging {< 0.1"} is a capability unique

to HST, yet one that could be lost at any any time.

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)

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL   

FGS GSacq               07                   07                   

FGS REacq               07                   07                

OBAD with Maneuver 30                   30              

SIGNIFICANT EVENTS: (None)