HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5087

PERIOD COVERED: 5am April 30 - 5am May 03, 2010 (DOY 120/09:00z-123/09:00z)

OBSERVATIONS SCHEDULED

WFC3/UV/IR 12021

An Irradiated Disk in an Ultraluminous X-Ray Source

Whether ultraluminous X-ray sources (ULXs) contain stellar-mass or

intermediate-mass black holes (IMBHs) is an important, but as yet

unresolved, astrophysical question. We have discovered variable optical

emission from the ULX NGC 5408 X-1 that we interpret as reprocessed

emission in an irradiated disk. We propose simultaneous observations

with Chandra and HST to test this interpretation and place constraints

on the geometry of the accretion disk. The observations should provide a

means to discriminate between stellar-mass versus intermediate-mass

black holes.

ACS/WFC 11995

CCD Daily Monitor (Part 2)

This program comprises basic tests for measuring the read noise and dark

current of the ACS WFC and for tracking the growth of hot pixels. The

recorded frames are used to create bias and dark reference images for

science data reduction and calibration. This program will be executed

four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To

facilitate scheduling, this program is split into three proposals. This

proposal covers 320 orbits (20 weeks) from 1 February 2010 to 20 June

2010.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more

reliably removed from science data using darks taken with the same

exposure sequences as the science data, than with a single dark current

image scaled by desired exposure time. Therefore, dark current images

must be collected using all sample sequences that will be used in

science observations. These observations will be used to monitor changes

in the dark current of the WFC3-IR channel on a day-to-day basis, and to

build calibration dark current ramps for each of the sample sequences to

be used by Gos in Cycle 17. For each sample sequence/array size

combination, a median ramp will be created and delivered to the

calibration database system (CDBS).

WFC3/UVIS/IR 11909

UVIS Hot Pixel Anneal

The on-orbit radiation environment of WFC3 will continually generate new

hot pixels. This proposal performs the procedure required for repairing

those hot pixels in the UVIS CCDs. During an anneal, the two-stage

thermo-electric cooler (TEC) is turned off and the four-stage TEC is

used as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of

the CCD warmup, a majority of the hot pixels will be fixed; previous

instruments such as WFPC2 and ACS have seen repair rates of about 80%.

Internal UVIS exposures are taken before and after each anneal, to allow

an assessment of the procedure's effectiveness in WFC3, provide a check

of bias, global dark current, and hot pixel levels, as well as support

hysteresis (bowtie) monitoring and CDBS reference file generation. One

IR dark is taken after each anneal, to provide a check of the IR

detector.

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the

UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.

Initially found via an unexpected bowtie-shaped feature in flatfield

ratios, subsequent lab tests on similar e2v devices have since shown

that it is also present as simply an overall offset across the entire

CCD, i.e., a QE offset without any discernable pattern. These lab tests

have further revealed that overexposing the detector to count levels

several times full well fills the traps and effectively neutralizes the

bowtie. Each visit in this proposal acquires a set of three 3x3 binned

internal flatfields: the first unsaturated image will be used to detect

any bowtie, the second, highly exposed image will neutralize the bowtie

if it is present, and the final image will allow for verification that

the bowtie is gone.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of

full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K

subarray biases are acquired at less frequent intervals throughout the

cycle to support subarray science observations. The internals from this

proposal, along with those from the anneal procedure (Proposal 11909),

will be used to generate the necessary superbias and superdark reference

files for the calibration pipeline (CDBS).

COS/FUV 11897

FUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity in each FUV

grating mode to detect any changes due to contamination or other causes.

COS/NUV 11896

NUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity of each NUV

grating mode to detect any changes due to contamination or other causes.

WFC3/ACS/UVIS 11877

HST Cycle 17 and Post-SM4 Optical Monitor

This program is the Cycle 17 implementation of the HST Optical

Monitoring Program.

The 36 orbits comprising this proposal will utilize ACS (Wide Field

Channel) and WFC3 (UVIS Channel) to observe stellar cluster members in

parallel with multiple exposures over an orbit. Phase retrieval

performed on the PSF in each image will be used to measure primarily

focus, with the ability to explore apparent coma, and astigmatism

changes in WFC3.

The goals of this program are to: 1) monitor the overall OTA focal

length for the purposes of maintaining focus within science tolerances

2) gain experience with the relative effectiveness of phase retrieval on

WFC3/UVIS PSFs 3) determine focus offset between the imagers and

identify any SI-specific focus behavior and dependencies

If need is determined, future visits will be modified to interleave

WFC3/IR channel and STIS/CCD focii measurements.

FGS 11875

Monitoring FGS2R2 Distortion and Alignment After SMOV4

This proposal monitors changes in the FGS2R2 distortion and alignment

after SMOV4 by observing selected stars in M35 in Position mode. Data

from each epoch are compared to track changes in FGS2R2. When the rate

of change becomes sufficiently slow, FGS2R2 will be cleared for a

mini-OFAD and FGS-FGS alignment calibration (carried out in another

phase 2 proposal).

STIS/CC 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,

and 1x1 at gain = 4, to build up high-S/N superbiases and track the

evolution of hot columns.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

FGS 11789

An Astrometric Calibration of Population II Distance Indicators

In 2002, HST produced a highly precise parallax for RR Lyrae. That

measurement resulted in an absolute magnitude, M(V)= 0.61+/-0.11, a

useful result, judged by the over ten refereed citations each year

since. It is, however, unsatisfactory to have the direct,

parallax-based, distance scale of Population II variables based on a

single star. We propose, therefore, to obtain the parallaxes of four

additional RR Lyrae stars and two Population II Cepheids, or W Vir

stars. The Population II Cepheids lie with the RR Lyrae stars on a

common K-band Period-Luminosity relation. Using these parallaxes to

inform that relationship, we anticipate a zero point error of 0.04

magnitude. This result should greatly strengthen confidence in the

Population II distance scale and increase our understanding of RR Lyrae

star and Pop. II Cepheid astrophysics.

STIS/CCD/MA1 11737

The Distance Dependence of the Interstellar N/O Abundance Ratio: A Gould

Belt Influence?

The degree of elemental abundance homogeneity in the interstellar medium

is a function of the enrichment and mixing processes that govern

galactic chemical evolution. Observations of young stars and the

interstellar gas within ~500 pc of the Sun have revealed a local ISM

that is so well-mixed it is having an impact on ideas regarding the

formation of extrasolar planets. However, the situation just beyond the

local ISM is not so clear. Sensitive UV absorption line measurements

have recently revealed a pattern of inhomogeneities in the interstellar

O, N, and Kr gas-phase abundances at distances of ~500 pc and beyond

that appear nucleosynthetic in origin rather than due to dust depletion.

In particular, based on a sample of 13 sightlines, Knauth et al. (2006)

have found that the nearby stars (d < 500 pc) exhibit a mean

interstellar N/O abundance ratio that is significantly higher (0.18 dex)

than that toward the more distant stars. Interestingly, all of their

sightlines lie in the sky vicinity of the Gould Belt of OB associations,

molecular clouds, and diffuse gas encircling the Sun at a distance of

~400 pc. Is it possible that mixing processes have not yet smoothed out

the recent ISM enrichment by massive stars in the young Belt region? By

measuring the interstellar N/O ratios in a strategic new sample of

sightlines with STIS, we propose to test the apparent N/O homogeneity

inside the Gould Belt and determine if the apparent decline in the N/O

ratio with distance is robust and associated with the Belt region.

WFC3/UV/IR 11709

Stretching the Diversity of Cosmic Explosions: The Supernovae of

Gamma-ray Bursts

While the association between gamma-ray bursts (GRBs) and massive stars

is robust, there is a large diversity of properties among supernovae

(SNe) associated with GRBs. The converse is also true: Several recent

events show that there is a large brightness range among high energy

transients associated with SNe. As part of a comprehensive program, we

propose to use HST in order to search for and characterize the SNe

associated with GRB.

HST offers the means to cleanly separate the light curve of the GRB

afterglow from the supernova, and to remove the contamination from the

host galaxy, opening a clear path to the fundamental parameters of the

SN, and thence to the progenitor. From these observations, we will

determine the absolute magnitude at maximum, the shape of the spectral

energy distribution, and any change over time of the energy

distribution. We will also measure the rate of decay of the exponential

tail.

Merged with the ground-based data that we will obtain for each event, we

will be able to compare our data set to models and constrain the energy

of the explosion, the mass of the ejecta and the mass of Nickel

synthesized during the explosion. These results will shed light on the

apparent variety of supernovae associated with gamma-ray bursts and

X-ray flashes, and on the relation between these SNe and other, more

common, types of core-collapse explosions.

COS/FUV 11687

SNAPing Coronal Iron

This is a Snapshot Survey to explore two forbidden lines of highly

ionized iron in late-type coronal sources. Fe XII 1349 (T~ 2 MK) and Fe

XXI 1354 (T~ 10 MK) -- well known to Solar Physics -- have been detected

in about a dozen cool stars, mainly with HST/STIS. The UV coronal

forbidden lines are important because they can be observed with velocity

resolution of better than 15 km/s, whereas even the state-of-the-art

X-ray spectrometers on Chandra can manage only 300 km/s in the kilovolt

band where lines of highly ionized iron more commonly are found. The

kinematic properties of hot coronal plasmas, which are of great interest

to theorists and modelers, thus only are accessible in the UV at

present. The bad news is that the UV coronal forbidden lines are faint,

and were captured only in very deep observations with STIS. The good

news is that 3rd-generation Cosmic Origins Spectrograph, slated for

installation in HST by SM4, in a mere 25 minute exposure with its G130M

mode can duplicate the sensitivity of a landmark 25-orbit STIS E140M

observation of AD Leo, easily the deepest such exposure of a late-type

star so far. Our goal is to build up understanding of the properties of

Fe XII and Fe XXI in additional objects beyond the current limited

sample: how the lineshapes depend on activity, whether large scale

velocity shifts can be detected, and whether the dynamical content of

the lines can be inverted to map the spatial morphology of the stellar

corona (as in "Doppler Imaging''). In other words, we want to bring to

bear in the coronal venue all the powerful tricks of spectroscopic

remote sensing, well in advance of the time that this will be possible

exploiting the corona's native X-ray radiation. The 1290-1430 band

captured by side A of G130M also contains a wide range of key plasma

diagnostics that form at temperatures from below 10, 000 K (neutral

lines of CNO), to above 200, 000 K (semi-permitted O V 1371), including

the important bright multiplets of C II at 1335 and Si IV at 1400;

yielding a diagnostic gold mine for the subcoronal atmosphere. Because

of the broad value of the SNAP spectra, beyond the coronal iron project,

we waive the normal proprietary rights.

WFC3/UVIS 11675

Stellar Forensics: A Post-Explosion View of the Progenitors of

Core-Collapse Supernovae

Recent studies have used high spatial resolution HST observations of SN

sites to identify the progenitors of core-collapse SNe on pre-explosion

images. These studies have set constraints about the nature of massive

stars and their evolution just prior to their explosion as SNe. Now, at

late-times when the SNe have faded sufficiently, it is possible to

return to the sites of these core-collapse SNe to search for clues about

the nature of their progenitors. We request time to conduct deep,

late-time, high-resolution imaging with ACS/HRC of the sites of six

core-collapse SNe. In this program we aim to: 1) confirm our

identifications, that were made with HST pre- explosion images, of the

red supergiant progenitors of four Type IIP SNe (1999ev, 2003gd, 2004A

and 2005cs), by observing if the objects identified as the progenitors

are now missing; 2) place precise constraints on the progenitor of the

Type Ic SN 2007gr by studying its host cluster; and 3) confirm our

identification of an LBV-like outburst of an unstable WR star as

belonging to the progenitor of a Type Ib-n core-collapse SN (2006jc),

using broad and narrow- band imaging to search for emission line stars

in its locality. The deep imaging will also allow to probe the stellar

populations in the immediate vicinities of these SNe, that were

previously obscured by the progenitors and the bright SNe. HST provides

the unique combination of high- resolution optical imaging at very faint

magnitudes that will facilitate this study.

WFC3/UV/IR 11664

The WFC3 Galactic Bulge Treasury Program: Populations, Formation

History, and Planets

Exploiting the full power of the Wide Field Camera 3 (WFC3), we propose

deep panchromatic imaging of four fields in the Galactic bulge. These

data will enable a sensitive dissection of its stellar populations,

using a new set of reddening-free photometric indices we have

constructed from broad-band filters across UV, optical, and near-IR

wavelengths. These indices will provide accurate temperatures and

metallicities for hundreds of thousands of individual bulge stars.

Proper motions of these stars derived from multi-epoch observations will

allow separation of pure bulge samples from foreground disk

contamination. Our catalogs of proper motions and panchromatic

photometry will support a wide range of bulge studies.

Using these photometric and astrometric tools, we will reconstruct the

detailed star-formation history as a function of position within the

bulge, and thus differentiate between rapid- and extended-formation

scenarios. We will also measure the dependence of the stellar mass

function on metallicity, revealing how the characteristic mass of star

formation varies with chemistry. Our sample of bulge stars with accurate

metallicities will include 12 candidate hosts of extrasolar planets.

Planet frequency is correlated with metallicity in the solar

neighborhood; our measurements will extend this knowledge to a remote

environment with a very distinct chemistry.

Our proposal also includes observations of six well-studied globular and

open star clusters; these observations will serve to calibrate our

photometric indices, provide empirical population templates, and

transform the theoretical isochrone libraries into the WFC3 filter

system. Besides enabling our own program, these products will provide

powerful new tools for a host of other stellar-population investigations

with HST/WFC3. We will deliver all of the products from this Treasury

Program to the community in a timely fashion.

WFC3/UV/ACS/WFC 11636

First Resolved Imaging of Escaping Lyman Continuum

The emission from star-forming galaxies appears to be responsible for

reionization of the universe at z > 6. However, the models that attempt

to describe the detailed impact of high-redshift galaxies on the

surrounding inter-galactic medium (IGM) are strongly dependent upon

several uncertain parameters. Perhaps the most uncertain is the fraction

of HI-ionizing photons produced by young stars that escape into the IGM.

Most attempts to measure this "escape fraction" have produced null

results. Recently, a small subset of z~3 Lyman Break Galaxies (LBGs) has

been found exhibiting large escape fractions. It remains unclear

however, what differentiates them from other LBGs. Several models

attempt to explain how such a large fraction of ionizing continuum can

escape through the HI and dust in the ISM (eg. "chimneys" created by SNe

winds, globular cluster formation, etc.), each producing unique

signatures which can be observed with resolved imaging of the escaping

Lyman continuum. To date, there are only six LBGs with individual

detections of escaping Lyman continuum at any redshift. We propose a

single deep, high resolution WFC3/UVIS image of the ionizing continuum

(F336W) and the rest-frame UV/optical (F606W/F814W/F160W) of five of

these six LBGs with large escape fractions. These LBGs have a high

surface density and large escape fractions, and lie at the optimal

redshift for Lyman continuum imaging with UVIS filters, making our

sample especially suitable for follow-up. With these data we will

discern the mechanisms responsible for producing large escape fractions,

and therefore gain insight into the process of reionization.

WFC3/UVIS 11628

Globular Cluster Candidates for Hosting a Central Black Hole

We are continuing our study of the dynamical properties of globular

clusters and we propose to obtain surface brightness profiles for high

concentration clusters. Our results to date show that the distribution

of central surface brightness slopes do not conform to standard models.

This has important implications for how they form and evolve, and

suggest the possible presence of central intermediate-mass black holes.

From our previous archival proposals (AR-9542 and AR- 10315), we find

that many high concentration globular clusters do not have flat cores or

steep central cusps, instead they show weak cusps. Numerical simulations

suggest that clusters with weak cusps may harbor intermediate-mass black

holes and we have one confirmation of this connection with omega

Centauri. This cluster shows a shallow cusp in its surface brightness

profile, while kinematical measurements suggest the presence of a black

hole in its center. Our goal is to extend these studies to a sample

containing 85% of the Galactic globular clusters with concentrations

higher than 1.7 and look for objects departing from isothermal behavior.

The ACS globular cluster survey (GO-10775) provides enough objects to

have an excellent coverage of a wide range of galactic clusters, but it

contains only a couple of the ones with high concentration. The proposed

sample consists of clusters whose light profile can only be adequately

measured from space-based imaging. This would take us close to

completeness for the high concentration cases and therefore provide a

more complete list of candidates for containing a central black hole.

The dataset will also be combined with our existing kinematic

measurements and enhanced with future kinematic studies to perform

detailed dynamical modeling.

STIS/CCD 11606

Dynamical Hypermassive Black Hole Masses

We will use STIS spectra to derive the masses of 5 hypermassive black

holes (HMBHs). From the observed scaling relations defined by less

massive spheroids, these objects are expected to reside at the nuclei of

host galaxies with stellar velocity dispersions greater than 320 km/s.

These 5 targets have confirmed regular gas distributions on the scales

of the black hole sphere of influence. It is essential that the sphere

of influence is resolved for accurate determinations of black hole mass

(0.1"). These scales cannot be effectively observed from the ground.

Only two HMBHs have had their masses modeled so far; it is impossible to

draw any general conclusions about the connections between HMBH mass and

their massive host galaxies. With these 5 targets we will determine

whether these HMBHs deviate from the scaling relations defined by less

massive spheroids. A larger sample will allow us to firmly anchor the

high mass end of the correlation between black hole mass and stellar

velocity dispersion, and other scaling relations. Therefore we are also

conducting a SNAPshot program with which we expect to detect a further

24 HMBH candidates for STIS observation in future cycles. At the

completion of this project we will have populated the high mass end of

the scaling relations with the sample sizes enjoyed by less massive

spheroids.

ACS/WFC3 11604

The Nuclear Structure of OH Megamaser Galaxies

We propose a snapshot survey of a complete sample of 80 OH megamaser

galaxies. Each galaxy will be imaged with the ACS/WFC through F814W and

a linear ramp filter (FR656N or FR716N or FR782N or FR853N) allowing us

to study both the spheroid and the gas morphology in Halpha + [N II]. We

will use the 9% ramps FR647M (5370-7570 angstroms) centered at 7000

angstroms and FR914M (7570-10, 719 angstroms) 8000 angstroms for

continuum subtraction for the high and low z objects respectively. OH

megamaser galaxies (OHMG) form an important class of ultraluminous

IR-galaxies (ULIRGs) whose maser lines emit QSO-like luminosities.

ULIRGs in general are associated with recent mergers but it is often

unclear whether their power output is dominated by starbursts or a

hidden QSO because of the high absorbing columns which hide their nuclei

even at X-ray wavelengths. In contrast, OHMG exhibit strong evidence for

the presence of an energetically important and recently triggered active

nucleus. In particular it is clear that much of the gas must have

already collapsed to form a nuclear disk which may be the progenitor of

a circum-nuclear torus, a key element of the unified scheme of AGN. A

great advantage of studying OHMG systems over the general ULIRG

population, is that the circum-nuclear disks are effectively "fixed" at

an inner, edge on, orientation, eliminating varying inclination as a

nuisance parameter. We will use the HST observations in conjunction with

existing maser and spectroscopic data to construct a detailed picture of

the circum-nuclear regions of a hitherto relatively neglected class of

galaxy that may hold the key to understanding the relationship between

galaxy mergers, nuclear star-formation, and the growth of massive black

holes and the triggering of nuclear activity.

ACS/WFC3 11599

Distances of Planetary Nebulae from SNAPshots of Resolved Companions

Reliable distances to individual planetary nebulae (PNe) in the Milky

Way are needed to advance our understanding of their spatial

distribution, birthrates, influence on galactic chemistry, and the

luminosities and evolutionary states of their central stars (CSPN). Few

PNe have good distances, however. One of the best ways to remedy this

problem is to find resolved physical companions to the CSPN and measure

their distances by photometric main-sequence fitting. We have previously

used HST to identify and measure probable companions to 10 CSPN, based

on angular separations and statistical arguments only. We now propose to

use HST to re-observe 48 PNe from that program for which additional

companions are possibly present. We then can use the added criterion of

common proper motion to confirm our original candidate companions and

identify new ones in cases that could not confidently be studied before.

We will image the region around each CSPN in the V and I bands, and in

some cases in the B band. Field stars that appear close to the CSPN by

chance will be revealed by their relative proper motion during the 13+

years since our original survey, leaving only genuine physical

companions in our improved and enlarged sample. This study will increase

the number of Galactic PNe with reliable distances by 50 percent and

improve the distances to PNe with previously known companions.

WFC3/UVIS 11594

A WFC3 Grism Survey for Lyman Limit Absorption at z=2

We propose to conduct a spectroscopic survey of Lyman limit absorbers at

redshifts 1.8 < z < 2.5, using WFC3 and the G280 grism. This proposal

intends to complete an approved Cycle 15 SNAP program (10878), which was

cut short due to the ACS failure. We have selected 64 quasars at 2.3 < z

< 2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar Sample, for

which no BAL signature is found at the QSO redshift and no strong metal

absorption lines are present at z > 2.3 along the lines of sight. The

survey has three main observational goals. First, we will determine the

redshift frequency dn/dz of the LLS over the column density range 16.0 <

log(NHI) < 20.3 cm^-2. Second, we will measure the column density

frequency distribution f(N) for the partial Lyman limit systems (PLLS)

over the column density range 16.0 < log(NHI) < 17.5 cm^-2. Third, we

will identify those sightlines which could provide a measurement of the

primordial D/H ratio. By carrying out this survey, we can also help

place meaningful constraints on two key quantities of cosmological

relevance. First, we will estimate the amount of metals in the LLS using

the f(N), and ground based observations of metal line transitions.

Second, by determining f(N) of the PLLS, we can constrain the amplitude

of the ionizing UV background at z~2 to a greater precision. This survey

is ideal for a snapshot observing program, because the on-object

integration times are all well below 30 minutes, and follow-up

observations from the ground require minimal telescope time due to the

QSO sample being bright.

ACS/WFC/WFC3/UV 11578

The Extremely Metal-Poor BCD Galaxy DDO 68: a Young Galaxy in the Local

Universe ?

A long standing question in astrophysics is the existence of young

galaxies, in which stars are now forming for the first time, in the

nearby (i.e., present-day) universe. Such galaxies would be the local

analogs of primordial galaxies observed at high redshift. The most

promising candidates have long been the most metal-poor systems,

including dwarf irregulars (dIrrs) and blue compact dwarfs (BCDs).

However, in many dIrrs and BCDs studied with HST an old (1 Gyr)

underlying stellar population, as traced by red giant branch (RGB)

stars, has been unambiguously detected. Even in I Zw 18, which is the

most-metal poor prototype of the class and long the most controversial

case, our group has recently succeeded in detecting an RGB. Nonetheless,

there remains the possibility that the star formation histories of

BCDs/dIrrs vary from galaxy to galaxy, and that truly young galaxies do

exist in the local universe. A new test of these issues has only

recently become possible with the identification of DDO 68 as an

extremely metal-poor galaxy with an oxygen abundance equal to that of I

Zw 18 (12+(O/H)=7.21). This galaxy is about a factor of 2-3 closer than

I Zw 18, which yields the opportunity to avoid the many ambiguities that

have plagued studies of I Zw 18. Also, DDO 68 resides in a void, making

it more likely that star formation has been suppressed for a very long

time. We will observe DDO 68 with ACS/WFC in F606W and F814W, plus F658N

(Halpha) to correct the broad F606W for gas contamination. We will use

WFC3 in parallel with the same filters to study radial population

gradients. Deep color-magnitude diagrams (CMDs) reaching the depth of

one magnitude below the predicted RGB tip will be constructed and

interpreted based on synthetic CMD fitting. These data will determine

unambiguously whether DDO 68 has an underlying old (RGB) stellar

population or is forming stars for the first time. Finding just a single

nearby ``young'' galaxy would have profound cosmological implications.

STIS/CCD 11567

Boron Abundances in Rapidly Rotating Early-B Stars

Models of rotation in early-B stars predict that rotationally driven

mixing should deplete surface boron abundances during the main-sequence

lifetime of many stars. However, recent work has shown that many boron

depleted stars are intrinsically slow rotators for which models predict

no depletion should have occurred, while observations of nitrogen in

some more rapidly rotating stars show less mixing than the models

predict. Boron can provide unique information on the earliest stages of

mixing in B stars, but previous surveys have been biased towards narrow-

lined stars because of the difficulty in measuring boron abundances in

rapidly rotating stars. The two targets observed as part of our Cycle 13

SNAP program 10175, just before STIS failed, demonstrate that it is

possible to make useful boron abundance measurements for early-B stars

with Vsin(i) above 100 km/s. We propose to extend that survey to a large

enough sample of stars to allow statistically significant tests of

models of rotational mixing in early-B stars.

NIC2/WFC3/IR 11548

Infrared Imaging of Protostars in the Orion A Cloud: The Role of

Environment in Star Formation

We propose NICMOS and WFC3/IR observations of a sample of 252 protostars

identified in the Orion A cloud with the Spitzer Space Telescope. These

observations will image the scattered light escaping the protostellar

envelopes, providing information on the shapes of outflow cavities, the

inclinations of the protostars, and the overall morphologies of the

envelopes. In addition, we ask for Spitzer time to obtain 55-95 micron

spectra of 75 of the protostars. Combining these new data with existing

3.6 to 70 micron photometry and forthcoming 5-40 micron spectra measured

with the Spitzer Space Telescope, we will determine the physical

properties of the protostars such as envelope density, luminosity,

infall rate, and outflow cavity opening angle. By examining how these

properties vary with stellar density (i.e. clusters vs. groups vs.

isolation) and the properties of the surrounding molecular cloud; we can

directly measure how the surrounding environment influences protostellar

evolution, and consequently, the formation of stars and planetary

systems. Ultimately, this data will guide the development of a theory of

protostellar evolution.

NIC3/WFC3/IR 11149

Characterizing the Stellar Populations in Lyman-Alpha Emitters and Lyman

Break Galaxies at 5.7<z<7 in the Subaru Deep Field

The epoch of reionization marks a major phase transition of the

Universe, during which the intergalactic space became transparent to UV

photons. Determining when this occurred and the physical processes

involved represents the latest frontier in observational cosmology. Over

the last few years, searches have intensified to identify the population

of high-redshift (z>6) galaxies that might be responsible for this

process, but the progress is hampered partly by the difficulty of

obtaining physical information (stellar mass, age, star formation

rate/history) for individual sources. This is because the number of z>6

galaxies that have both secure spectroscopic redshifts and high-quality

infrared photometry (especially with Spitzer/IRAC) is still fairly

small. Considering that only several photometric points are available

per source, and that many model SEDs are highly degenerate, it is

crucial to obtain as many observational constraints as possible for each

source to ensure the validity of SED modeling. To better understand the

physical properties of high-redshift galaxies, we propose here to

conduct HST/NICMOS (72 orbits) and Spitzer/IRAC (102 hours) imaging of

spectroscopically confirmed, bright (z<26 mag (AB)) Ly-alpha emitters

(LAEs) and Lyman-break galaxies (LBGs) at 5.7<z<7 selected from the

Subaru Deep Field. Spectroscopic redshifts remove one critical free

parameter from SED modeling while bright source magnitudes ensure

high-quality photometric data. By making accurate determinations of

stellar masses, ages, and star-formation histories, we will specifically

address the following major questions: (1) Do LAEs and LBGs represent

physically different galaxy populations at z>6 as suggested recently?

(2) Is Ly-alpha emission systematically suppressed at z>6 with respect

to continuum emission? (i.e., are we reaching the epoch of incomplete

reionization?), and (3) Do we see any sign of abnormally young stellar

population in any of the z>6 galaxies?

WFC3/ACS/IR 11142

Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3<z<2.7

Using HST and Spitzer

We aim to determine physical properties of IR luminous galaxies at

0.3<z<2.7 by requesting coordinated HST/NIC2 and MIPS 70um observations

of a unique, 24um flux-limited sample with complete Spitzer mid-IR

spectroscopy. The 150 sources investigated in this program have S(24um)

> 0.8mJy and their mid-IR spectra have already provided the majority

targets with spectroscopic redshifts (0.3<z<2.7). The proposed

150~orbits of NIC2 and 66~hours of MIPS 70um will provide the physical

measurements of the light distribution at the rest-frame ~8000A and

better estimates of the bolometric luminosity. Combining these

parameters together with the rich suite of spectral diagnostics from the

mid-IR spectra, we will (1) measure how common mergers are among LIRGs

and ULIRGs at 0.3<z<2.7, and establish if major mergers are the drivers

of z>1 ULIRGs, as in the local Universe, (2) study the co-evolution of

star formation and blackhole accretion by investigating the relations

between the fraction of starburst/AGN measured from mid-IR spectra vs.

HST morphologies, L(bol) and z, and (3) obtain the current best

estimates of the far-IR emission, thus L(bol) for this sample, and

establish if the relative contribution of mid-to-far IR dust emission is

correlated with morphology (resolved vs. unresolved).

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              25            25

FGS REAcq              22            22

OBAD with Maneuver 22           22

SIGNIFICANT EVENTS: (None)