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      # 4346

PERIOD COVERED: UT April 20,21,22, 2007 (DOY 110,111,112,)

OBSERVATIONS SCHEDULED

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.

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.

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.

ACS/SBC 11050

ACS UV contamination monitor

The observations consist of imaging and spectroscopy with SBC of the

cluster NGC 6681 in order to monitor the temporal evolution of the UV

sensitivity of the SBC.

WFPC2 11002

A Census of LIRGs in Clusters of Galaxies in the First Half of the

Universe from the IRAC Shallow Survey

The incidence of LIRGs and ULIRGs is roughly two orders of magnitude

higher in the field at redshift z > 1, and at these redshifts such

objects dominate the global star formation activity. Mergers which fuel

such activity might be expected to enhance the frequency of LIRGs in

dense environments. We propose to use MIPS to obtain a census of LIRGs

in z > 1 galaxy clusters from a well defined sample found in the IRAC

Shallow Survey. Supporting IRAC and HST ACS data are also requested.

NIC3 10899

Identifying z>7 galaxies from J-dropouts

NICMOS Parallel Imaging campaigns covered enough sky {250 pointings}

with enough sensitivity in the 110W and 160W filters to identify 6

extremely red resolved sources which are prime candidates for J-band

dropouts. Their complete absence of detectable J band flux can be caused

by an opaque Lyman cut-off at z=8-10. We propose to followup these

candidates with NICMOS imaging and jointly propose Spitzer IRAC

photometry. Deep F110W and Spitzer/IRAC 3.5/4.8 micron imaging will

confirm if any of these candidates are indeed Lyman Break galaxies

observed less than 500 Myrs after the Big Bang. Genuine LBGs will remain

undetected in F110W, while being detected with flat spectra in the IRAC

bands. The combined SED will provide information about the stellar mass

of these galaxies, and the possible presence of evolved stars or dust

reddening. The proposed observations will be sensitive enough to detect

the F110W flux from galaxies as red as {J- H}=2.8 {AB mags, 5 sigma}. If

any of the candidates are detected with bluer colors, they will most

likely be exceptional "Distant Red Galaxies" at z of 4 to 6. The

proposed data will constrain the stellar populations of these

extraordinarily red galaxies, which would be candidates for the

earliest, most massive galaxies which formed.

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.

NIC1 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the thick

disks and halos of seven nearby, massive, edge-on galaxies using ACS,

NICMOS, and WFPC2 in parallel. These observations will provide accurate

star counts and color-magnitude diagrams 1.5 magnitudes below the tip of

the Red Giant Branch sampled along the two principal axes and one

intermediate axis of each galaxy. We will measure the metallicity

distribution functions and stellar density profiles from star counts

down to very low average surface brightnesses, equivalent to ~32 V-mag

per square arcsec. These observations will provide the definitive HST

study of extra-planar stellar populations of spiral galaxies. Our

targets cover a range in galaxy mass, luminosity, and morphology and as

function of these galaxy properties we will provide: - The first

systematic study of the radial and isophotal shapes of the diffuse

stellar halos of spiral galaxies - The most detailed comparative study

to date of thick disk morphologies and stellar populations - A

comprehensive analysis of halo and thick disk metallicity distributions

as a function of galaxy type and position within the galaxy. - A

sensitive search for tidal streams - The first opportunity to directly

relate globular cluster systems to their field stellar population We

will use these fossil records of the galaxy assembly process preserved

in the old stellar populations to test halo and thick disk formation

models within the hierarchical galaxy formation scheme. We will test

LambdaCDM predictions on sub-galactic scales, where it is difficult to

test using CMB and galaxy redshift surveys, and where it faces its most

serious difficulties.

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.

WFPC2 10884

The Dynamical Structure of Ellipticals in the Coma and Abell 262

Clusters

We propose to obtain images of 13 relatively luminous early type

galaxies in the Coma cluster and Abell 262 for which we have already

collected ground based major and minor axis spectra and images. The

higher resolution HST images will enable us to study the central regions

of these galaxies which is crucial to our dynamical modelling. The

complete data set will allow us to perform a full dynamical analysis and

to derive the dark matter content and distribution, the stellar orbital

structure, and the stellar population properties of these objects,

probing the predictions of galaxy formation models. The dynamical

analysis will be performed using an up-to-date axi-symmetric orbit

superposition code.

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 10845

HUNTING FOR OPTICAL COMPANIONS TO BINARY MILLISECOND PULSARS IN TERZAN 5

AND NGC6266

We propose deep WFPC2 and NICMOS observations to search for optical

companions to binary millisecond pulsar {MSPs} in two Globular Clusters

{GCs}: Terzan 5 and NGC6266. Terzan 5 has the largest MSP population of

any GC: 33 MSP {17 in binary systems} have been discovered up to now in

this stellar system. NGC6266 ranks fifth among the GC for wealth of MSPs

but it is the only one in which all the {six} detected MSPs are in

binary systems. Only 5 optical counterparts to binary MSP companions are

known in GCs {two of them have been discovered by our group}: hence even

the addition of a few new identifications are crucial to investigate the

variety of processes occurring in binary MSPs in dense environment. The

observations proposed here would easily double/triple the existing

sample of known MSP companions, allowing the first meaningful study of

the phenomena which drive the formation and evolution of these exotic

systems. Moreover, since most of binary MSP in GC are formed via stellar

interactions in the high density regions of the cluster, the

determination of the nature of the companion and the incidence of this

collisionally induced population have a significant impact on our

knowledge of the cluster dynamics. Even more interesting, the study of

the optical companions to NSs in a GC allows to derive tighter

constraints {than those obtainable for NS binaries in the galactic

field} on the properties {mass, orbital inclination and so on} of the

compation star. This has, in turn, an intrisic importance for

fundamental physics since it offers the opportunity of measuring the

mass of the NS and hence to put constraints to the equation of state of

matter at nuclear equilibrium density.

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.

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 10798

Dark Halos and Substructure from Arcs & Einstein Rings

The surface brightness distribution of extended gravitationally lensed

arcs and Einstein rings contains super-resolved information about the

lensed object, and, more excitingly, about the smooth and clumpy mass

distribution of the lens galaxies. The source and lens information can

non-parametrically be separated, resulting in a direct "gravitational

image" of the inner mass-distribution of cosmologically-distant galaxies

{Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}. With this goal

in mind, we propose deep HST ACS-F555W/F814W and NICMOS-F160W WFC

imaging of 20 new gravitational-lens systems with spatially resolved

lensed sources, of the 35 new lens systems discovered by the Sloan Lens

ACS Survey {Bolton et al. 2005} so far, 15 of which are being imaged in

Cycle-14. Each system has been selected from the SDSS and confirmed in

two time- efficient HST-ACS snapshot programs {cycle 13&14}.

High-fidelity multi-color HST images are required {not delivered by the

420s snapshots} to isolate these lensed images {properly cleaned,

dithered and extinction-corrected} from the lens galaxy surface

brightness distribution, and apply our "gravitational maging" technique.

Our sample of 35 early-type lens galaxies to date is by far the largest,

still growing, and most uniformly selected. This minimizes selection

biases and small-number statistics, compared to smaller, often

serendipitously discovered, samples. Moreover, using the WFC provides

information on the field around the lens, higher S/N and a better

understood PSF, compared with the HRC, and one retains high spatial

resolution through drizzling. The sample of galaxy mass distributions -

determined through this method from the arcs and Einstein ring HST

images - will be studied to: {i} measure the smooth mass distribution of

the lens galaxies {dark and luminous mass are separated using the HST

images and the stellar M/L values derived from a joint stellar-dynamical

analysis of each system}; {ii} quantify statistically and individually

the incidence of mass-substructure {with or without obvious luminous

counter- parts such as dwarf galaxies}. Since dark-matter substructure

could be more prevalent at higher redshift, both results provide a

direct test of this prediction of the CDM hierarchical

structure-formation model.

WFPC2 10786

Rotational state and composition of Pluto's outer satellites

We propose an intricate set of observations aimed at discovering the

rotational state of the newly discovered satellites of Pluto, S/2005 P1

and S/2005 P2. These observations will indicate if the satellites are in

synchronous rotation or not. If they are not, then the observations will

determine the rotational period or provide tight constraints on the

amplitude. The other primary goal is to extend the wavelength coverage

of the colors of the surface and allow us to constrain the surface

compositions of both objects. From these data we will also be able to

significantly improve the orbits of P1 and P2, improve the measurement

of the bulk density of Charon, and search for albedo changes on the

surface of Pluto.

WFPC2 10524

Blue Stragglers: a key stellar population to probe internal cluster

dynamics

This proposal is part of a coordinated project devoted to understand the

interplay of globular cluster {GC} dynamics and the formation and

evolution of blue straggler stars {BSS}. By using a combination of HST

and ground-based observations we are constructing complete BSS surveys

in a sample of GCs; complete BSS surveys require mid-UV HST observations

in the center and wide field CCD ground based observations under

excellent seeing conditions of the exterior. Up to now only four

clusters have been surveyed in this way and the results are surprising:

in three GCs {M3, 47 Tuc, NGC 6752} we have discovered that the BSS

radial distribution is bimodal, highly peaked in the cluster center,

rapidly decreasing at intermediate radii and rising again at large radii

{Ferraro et al. 1997, 2004, Sabbi et al. 2004}, conversely BSS

population in Omega Centauri does not show any signature of the

segregation which would be expected for a class of objects arising from

either stellar interactions or binarity {Ferraro et al. 2005}. These

observational facts are opening a new prospective in the study of the

formation processes and evolution of BSS in GCs. By using extensive

simulations, we demonstrated that the spatial distribution of BSS

observed in 47 Tuc can be only reproduced if a sizable fraction of BSS

is generated {via mass transfer in primordial binaries} in the

peripheral region of the cluster {Mapelli et al 2004}, thus excluding a

purely collisional formation scenario. Here we propose mid-UV imaging of

a few clusters suspected of harboring a large population of central BSS

and a few known to have many BSS the external region. These are good

candidates for determining accurate BSS radial distributions. The modest

amount of time proposed here will go far to determine the ubiquity of

BSS bimodality and to constrain models of dynamical evolution. Since we

believe the proposed observations would be useful to the entire stellar

community {for multifold purposes} we waive the propretary period.

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               28                  28          

FGS REacq               14                  14                

OBAD with Maneuver 84                  84               

SIGNIFICANT EVENTS: (None)