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      # 4345

PERIOD COVERED: UT April 19, 2007 (DOY 109)

OBSERVATIONS SCHEDULED

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.

WFPC2 10809

The nature of "dry" mergers in the nearby Universe

Recent studies have shown that "dry" mergers of red, bulge-dominated

galaxies at low redshift play an important role in shaping today's most

massive ellipticals. These mergers have been identified in extremely

deep ground-based images of red sequence galaxies at z ~ 0.1. The

ground-based images reach surface brightness limits of AB ~ 29, but lack

the resolution to study the morphologies of the galaxies inside the

effective radius. Here we propose to obtain ACS images of a

representative sample of 40 of these red sequence galaxies: 15 ongoing

dry mergers, 15 remnants, and 10 undisturbed objects. We will measure

the isophote shapes and ellipticities of the galaxies, their dust

content, morphological fine structure {shells and ripples}, AGN content,

and their location on the Fundamental Plane. By comparing galaxies in

different stages of the merging process we can constrain the amount of

gas associated with these red mergers, the effect of active nuclei, and

track structural changes. As two galaxies can be observed in a single

orbit 20 orbits are requested to observe the 40 galaxies.

WFPC2 10829

Secular Evolution at the End of the Hubble Sequence

The bulgeless disk galaxies at the end of the Hubble Sequence evolve at

a glacial pace relative to their more violent, earlier-type cousins. The

causes of their internal, or secular evolution are important because

secular evolution represents the future fate of all galaxies in our

accelerating Universe and is a key ingredient to understanding galaxy

evolution in lower-density environments at present. The rate of secular

evolution is largely determined by the stability of the cold ISM against

collapse, star formation, and the buildup of a central bulge. Key

diagnostics of the ISM's stability are the presence of compact molecular

clouds and narrow dust lanes. Surprisingly, edge-on, pure disk galaxies

with circular velocities below 120 km/s do not appear to contain such

dust lanes. We propose to obtain ACS/WFC F606W images of a well-selected

sample of extremely late-type disk galaxies to measure the

characteristic scale size of the cold ISM and determine if they possess

the unstable, cold ISM necessary to drive secular evolution. Our sample

has been carefully constructed to include disk galaxies above and below

the critical circular velocity of 120 km/s where the dust properties of

edge-on disks change so remarkably. We will then use surface brightness

profiles to search for nuclear star clusters and pseudobulges, which are

early indicators that secular evolution is at work, as well as measure

the pitch angle of the dust lanes as a function of radius to estimate

the central mass concentrations.

FGS 10931

Dynamical Masses and Radii of Four White Dwarf Stars

We will use FGS1R in its high angular resolution observing mode (TRANS)

to resolve the white dwarf binary systems. Each exposure will be comprised

of about 20 scans. The interferograms derived from each scan will be cross-

correlated and co-added to yield a high SNR. To further surpress the

noise (these targets are near the FGS's faint limiting magnitude), the

co-added inteferograms will be carefully smoothed by being represented as a

piece-wise We will use FGS1R in its high angular resolution observing

mode (TRANS) to resolve the white dwarf binary systems. Each exposure

will be comprised of about 20 scans. The interferograms derived from

each scan will be cross-correlated and co-added to yield a high SNR. To

further surpress the noise(these targets are near the FGS's faint

limiting magnitude), the co-added inteferograms will be carefully

smoothed by being represented as a piece-wise smooth segmanted

polynomial. These observations will yield the separation and position

angle of the binary components, as well as the brightness of each. In

addition, the binary and field stars simultaneously in the FGS FOV will

be observed in POS mode to accurately determine the relative positions

of the stars. This will facilitate the construction of an inertial

reference frame for the binary, thereby allowing the relative orbit that

will be ultimately determined from the TRANS data to be converted into a

physical orbit. This will allow us to determine the relative mass of

each white dwarf in the binarty system. In addition, the POS mode data

will give the proper motion and parallax of the binary, which will allow

us to compute the mass and radius of each white dwarf.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new proceedure proposed to alleviate the CR-persistence problem of

NICMOS. Dark frames will be obtained immediately upon exiting the SAA

contour 23, and everytime 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 i

mages. Each observation will need its own CRMAP, as different SAA

passages leave different imprints on the NICMOS detectors.

NIC3 10792

Quasars at Redshift z=6 and Early Star Formation History

We propose to observe four high-redshift quasars {z=6} in the NIR in

order to estimate relative Fe/Mg abundances and the central black hole

mass. The results of this study will critically constrain models of

joint quasar and galaxy formation, early star formation, and the growth

of supermassive black holes. Different time scales and yields for

alpha-elements {like O or Mg} and for iron result into an iron

enrichment delay of ~0.3 to 0.6 Gyr. Hence, despite the well-known

complexity of the FeII emission line spectrum, the ratio iron/alpha -

element is a potentially useful cosmological clock. The central black

hole mass will be estimated based on a recently revised back hole mass -

luminosity relationship. The time delay of the iron enrichment and the

time required to form a supermassive black hole {logM>8 Msol, tau

~0.5Gyr} as evidenced by quasar activity will be used to date the

beginning of the first intense star formation, marking the formation of

the first massive galaxies that host luminous quasars, and to constrain

the epoch when supermassive black holes start to grow by accretion.

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 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:

10781 - GSAcq(1,3,1) was not attempted due to prior M2G entry

           GSacq(1,3,1) scheduled at 109/15:24:49 - 15:32:54 was not attempted.

           Open loop period(s), following the second of a pair of OBADs resulted in

           unplanned M2G entry. OBAD2 had (RSS) value of 120.38 arcseconds. Because

           the OBAD2 was reset, the acquisition was not attempted. Post-acquisition

           OBAD/MAP had (RSS) value of 2130.60 arcseconds.

10782 - GSacq (1,2,2) loss of lock

           During LOS GSacq(1,2,2) scheduled at 110/04:22:51 loss lock. At

           AOS(04:50:02) stop flags QF1STOPF and QSTOP were flagging.

COMPLETED OPS REQUEST:

10837-3 - HMSS/CSS KF Initialization Convergence

18041-0 - Preview KF Sun Vector data via TMDiags

17597-7 - FHST Stuck-on-Bottom Macro Execution

COMPLETED OPS NOTES: (None)

SIGNIFICANT EVENTS:

Flish Report

The Kalman Filter was restarted at 109/21:48 during orbit day and during

an M2G guiding interval. The filter was activated with the default

configuration of MSS and CSS sensor inputs enabled. All UKF parameters

showed nominal convergence and steady-state operation. The test was an

MSS/CSS Initialization Test Case with the spacecraft inertially fixed

during a slow changing B-field in orbit day (M_C_INS, Test #8). The

Kalman Filter was restarted at 109/23:34 during orbit day, an M2G

guiding interval and a large vehicle slew. The filter was activated with

the default configuration of MSS and CSS sensor inputs enabled. All UKF

parameters showed nominal convergence and steady-state operation. The

test was an MSS/CSS Initialization Test Case with the spacecraft

maneuvering during a slow changing B-field in orbit day (M_C_IVS, Test

#6).

This completes the KF OOT testing for this week.