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Daily Report #5175



 
 
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Old September 7th 10, 06:01 PM posted to sci.astro.hubble
Cooper, Joe
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Posts: 568
Default Daily Report #5175

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5175

PERIOD COVERED: 5am September 3 - 5am September 7, 2010 (DOY 246/09:00z-249/09:00z)

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

12376 - GSAcq(1,2,1) scheduled at 246/17:10:16z required two attempts
to achieve FL-DV on FGS-1.

Observations possibly affected: STIS 69 proposal ID#11668, ACS 77-78 proposal ID#11882

12377 - REAcq(1,2,1) Fails 2 Attempts, Fine Lock on 3rd Attempt @
246/20:22z

Observations possibly affected: WFC3 170-171 proposal #11914, STIS 72
proposal #11668

12378 - GSAcq(2,1,1)scheduled at 248/03:04:13 resulted in fine lock
backup on FGS2(2,0,2).

Observations possibly affected: ACS 104 proposal ID#11996, WFC3 234
and 235 proposal ID#11594, WFC3 2-3 proposal ID#11905

12381 ? GSAcq(1,2,1) Failed 1st Attempt, Fine lock on 2nd @
249/12:16:37z

Observations possibly affected: STIS 9 proposal ID#11668


COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 28 28
FGS REAcq 33 33
OBAD with Maneuver 25 25

SIGNIFICANT EVENTS: (None)


OBSERVATIONS SCHEDULED:

WFC3/UV 12232

Detection and Mass Measurement of an Isolated Brown

We propose observations that are likely to detect the brown dwarf lens
object for microlensing event MACHO-179-A, which was observed by the
MACHO collaboration some 15 years ago. The strong microlensing
parallax signal seen in the light curve and follow-up Keck adaptive
optics images imply that the lens is a brown dwarf within about 300
parsecs. If the lens object is at least as massive as 0.015 Solar
masses at an age of 1 Gyr or 0.03 Solar masses at an age of 10 Gyr,
these observations will detect the lens and measure its relative
lens-source proper motion. The relative proper motion can be combined
with the microlensing parallax measurement and a precise WFC3/UVIS
measurement of the source star brightness to yield a mass measurement
of the source star to 3% or better.

WFC3/IR 12217

Spectroscopy of Faint T Dwarf Calibrators: Understanding the
Substellar Mass Function and the Coolest Brown Dwarfs

More than 100 methane brown dwarfs, or T dwarfs, have now been
discovered in the local field with 2MASS, SLOAN and UKIDSS, opening up
a new area of physics describing objects at 450-1400 K. However, very
few calibrator objects exist with well established ages and
metallicities. A very surprising result from the UKIDSS sample
(supported by 2MASS and SLOAN) is that the substellar mass function in
the local field appears to decline to lower masses, in marked contrast
to the rising initial mass function (IMF) observed in young clusters.
Given that such a difference between the present day IMF and the
Galactic time-averaged IMF is unlikely, it is very possible that the
apparently falling IMF is an artifact of serious errors in either T
model atmospheres or the evolutionary isochrones. We propose WFC3
spectroscopy of 4 faint T dwarf calibrators with well established ages
and metallicities in the Pleiades and Sigma Ori clusters, and 2 faint
field T dwarfs from UKIDSS for comparison. These spectra will
constitute vital calibration data for T dwarf atmospheres with a wide
range of surface gravities, which will be used to test and improve the
model atmospheres. They will also aid preparation for future
spectroscopy of the much larger numbers of field T dwarfs to soon be
found by VISTA and WISE. These new surveys will permit a more precise
measurement of the mass function and detection of even cooler objects.

WFC3/UV 12091

WFC3/UVIS Fringe Calibration - Part 2

Fringing has been observed in flat fields of 12 narrowband filters (4
full-frame and 3 quad spectral elements) longer than 600 nm, with
peak-to-peak fringe amplitude variations ranging from 0.5% to 14.2%
(WFC3 ISR 2010-04). Two filters (F953N and F656N) will be tested in
program 11922, supporting 88 Cycle 17 GO exposures in these filters.
Here we propose to observe globular cluster Omega Centauri (NGC 5139)
in the other 10 filters affected by fringing, supporting 319 Cycle 17
GO exposures in these filters. By measuring the relative changes in
brightness of stars at different positions on the detector, we will
determine the local variations induced by the fringing pattern.

The data will serve two purposes: characterize the effect of fringing
on photometry of on-orbit data, and verify models used to correct for
fringing effects. The models rely on Thermal Vacuum Test 3 (TV3) data
between 845-990 nm and NASA/GSFC Detector Characterization Laboratory
(DCL) test data from 700-1060 nm. Only the F953N filter in program
11922 overlaps with the test data wavelength range, making it
difficult to compare the efficacy of fringe models. This program will
expand the on-orbit fringing data so that we can compare models at 6
new wavelengths within the ground test data wavelength range, as well
as 4 new wavelengths not covered by the ground test data. Flight data
in these 4 filters can be corrected by extrapolating the model beyond
the wavelength range of the test data used to create the model.

COS/FUV 12083

COS G140L/1280 lamp template

This is an internal only program that obtains lamp template spectra
with the G140L grating at all FPPOS, using the new cenwave 1280. This
new cenwave will be available to users starting in Cycle 18. Data
obtained in this program will be used to update the FUV lamp template
reference file. We follow the same procedure following during SMOV
when obtaining lamp template spectra, i.e., to allow any mechanism
drift to settle the first exposure is 1800 sec long, with the lamp
flashed at regular intervals.

Note that this program can only be executed after FSW changes have
been made (current estimate for these FSW changes is ~Aug 2010
timeframe), as this mode is not yet implemented.

S/C 12046

COS FUV DCE Memory Dump

Whenever the FUV detector high voltage is on, count rate and current
draw information is collected, monitored, and saved to DCE memory.
Every 10 msec the detector samples the currents from the HV power
supplies (HVIA, HVIB) and the AUX power supply (AUXI). The last 1000
samples are saved in memory, along with a histogram of the number of
occurrences of each current value.

In the case of a HV transient (known as a "crackle" on FUSE), where
one of these currents exceeds a preset threshold for a persistence
time, the HV will shut down, and the DCE memory will be dumped and
examined as part of the recovery procedure. However, if the current
exceeds the threshold for less than the persistence time (a
"mini-crackle" in FUSE parlance), there is no way to know without
dumping DCE memory. By dumping and examining the histograms regularly,
we will be able to monitor any changes in the rate of "mini-crackles"
and thus learn something about the state of the detector.

COS/NUV/FUV 12034

COS-GTO: Brown Dwarf Activity Part 2

Based on the Findings in our Cycle 17 program, we will focus on
M-stars in Cycle 18.

WFC3/UV 12019

After the Fall: Fading AGN in Post-starburst Galaxies

We propose joint Chandra and HST observations of an extraordinary
sample of 12 massive post-starburst galaxies at z=0.4-0.8 that are in
the short-lived evolution phase a few 100 Myr after the peak of
merger-driven star formation and AGN activity. We will use the data to
measure X-ray luminosities, black hole masses, and accretion rates;
and with the accurate "clocks" provided by post-starburst stellar
populations, we will directly test theoretical models that predict a
power-law decay in the AGN light curve. We will also test whether star
formation and black hole accretion shut down in lock-step, quantify
whether the black holes transition to radiatively inefficient
accretion states, and constrain the observational signatures of black
hole mergers.

WFC3/UVIS 12018

Ultra-Luminous X-Ray Sources in the Most Metal-Poor Galaxies

There is growing observational and theoretical evidence to suggest
that Ultra-Luminous X-ray sources (ULX) form preferentially in low
metallicity environments. Here we propose a survey of 27 nearby (
30Mpc) star-forming Extremely Metal Poor Galaxies (Z5% solar). There
are almost no X-ray observations of such low abundance galaxies (3 in
the Chandra archive). These are the most metal-deficient galaxies
known, and a logical place to find ULX if they favor metal-poor
systems. We plan to test recent population synthesis models which
predict that ULX should be very numerous in metal-poor galaxies. We
will also test the hypothesis that ULX form in massive young star
clusters, and ask for HST time to obtain the necessary imaging data.

WFC3/UV 12008

Primordial formation of Close Binaries in Globular Clusters with Low
Density Cores

The primordial binary population is a key input parameter for any
realistic model of dense star cluster dynamics. However, the number of
primordial binaries and its direct implications for the formation rate
of close binaries remain poorly understood. Theoretical calculations
show that cataclysmic variables can be formed directly from primordial
binaries in or near the core of low core density globular clusters. We
propose to use Chandra/HST to study low density core globular clusters
systematically and to test the prediction that low-luminosity X-ray
sources can be formed from primordial binaries in the cluster core.
This project will complement our successful Chandra/HST program to
study the dynamical formation of X-ray sources in high core density
globular clusters.

ACS/WFC 11996

CCD Daily Monitor (Part 3)

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 308 orbits (19.25 weeks) from 21 June
2010 to 1 November 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/IR 11928

WFC3/IR Low-Frequency Flat and Geometric Distortion

Multiple observations of globular cluster Omega Cen at multiple
infrared wavelengths of IR detector will be used to derive filter
dependency of low-frequency sensitivity (L_flat fields) across of IR
detector and its time variation. Additionally, the same data will be
also used to derive filter-dependant geometric distortion of the
detector and its time-dependency.

WFC3/UVIS 11914

UVIS Earth Flats

This program is an experimental path finder for Cycle 18 calibration.
Visible-wavelength flat fields will be obtained by observing the dark
side of the Earth during periods of full moon illumination. The
observations will consist of full-frame streaked WFC3 UVIS imagery:
per 22- min total exposure time in a single "dark-sky" orbit, we
anticipate collecting 7000 e/pix in F606W or 4500 e/pix in F814W. To
achieve Poisson S/N 100 per pixel, we require at least 2 orbits of
F606W and 3 orbits of F814W.

For UVIS narrowband filters, exposures of 1 sec typically do not
saturate on the sunlit Earth, so we will take sunlit Earth flats for
three of the more-commonly used narrowband filters in Cycle 17 plus
the also-popular long-wavelength quad filters, for which we get four
filters at once.

Why not use the Sunlit Earth for the wideband visible-light filters?
It is too bright in the visible for WFC3 UVIS minimum exposure time of
0.5 sec. Similarly, for NICMOS the sunlit-Earth is too bright which
saturates the detector too quickly and/or induces abnormal behaviors
such as super-shading (Gilmore 1998, NIC 098-011). In the narrowband
visible and broadband near- UV its not too bright (predictions in Cox
et al. 1987 "Standard Astronomical Sources for HST: 6. Spatially Flat
Fields." and observations in ACS Program 10050).

Other possibilities? Cox et al.'s Section II.D addresses many other
possible sources for flat fields, rejecting them for a variety of
reasons. A remaining possibility would be the totally eclipsed moon.
Such eclipses provide approximately 2 hours (1 HST orbit) of
opportunity per year, so they are too rare to be generically useful.
An advantage of the moon over the Earth is that the moon subtends less
than 0.25 square degree, whereas the Earth subtends a steradian or
more, so scattered light and light potentially leaking around the
shutter presents additional problems for the Earth. Also, we're unsure
if HST can point 180 deg from the Sun.

WFC3/UVIS 11912

UVIS Internal Flats

This proposal will be used to assess the stability of the flat field
structure for the UVIS detector throughout the 15 months of Cycle 17.
The data will be used to generate on-orbit updates for the delta-flat
field reference files used in the WFC3 calibration pipeline, if
significant changes in the flat structure are seen.

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 11895

FUV Detector Dark Monitor

Monitor the FUV detector dark rate by taking long science exposures
without illuminating the detector. The detector dark rate and spatial
distribution of counts will be compared to pre-launch and SMOV data in
order to verify the nominal operation of the detector. Variations of
count rate as a function of orbital position will be analyzed to find
dependence of dark rate on proximity to the SAA. Dependence of dark
rate as function of time will also be tracked.

COS/NUV 11894

NUV Detector Dark Monitor

The purpose of this proposal is to measure the NUV detector dark rate
by taking long science exposures with no light on the detector. The
detector dark rate and spatial distribution of counts will be compared
to pre-launch and SMOV data in order to verify the nominal operation
of the detector. Variations of count rate as a function of orbital
position will be analyzed to find dependence of dark rate on proximity
to the SAA. Dependence of dark rate as function of time will also be
tracked.

ACS/WFC3 11882

CCD Hot Pixel Annealing

This program continues the monthly anneal that has taken place every
four weeks for the last three cycles. We now obtain WFC biases and
darks before and after the anneal in the same sequence as is done for
the ACS daily monitor (now done 4 times per week). So the anneal
observation supplements the monitor observation sets during the
appropriate week. Extended Pixel Edge Response (EPER) and First Pixel
Response (FPR) data will be obtained over a range of signal levels for
the Wide Field Channel (WFC). This program emulates the ACS pre-flight
ground calibration and post-launch SMOV testing (program 8948), so
that results from each epoch can be directly compared. The High
Resolution Channel (HRC) visits have been removed since it could not
be repaired during SM4.

This program also assesses the read noise, bias structure, and
amplifier cross-talk of ACS/WFC using the GAIN=1.4 A/D conversion
setting. This investigation serves as a precursor to a more
comprehensive study of WFC performance using GAIN=1.4.

STIS/CCD 11849

STIS CCD Hot Pixel Annealing

This purpose of this activity is to repair radiation induced hot pixel
damage to the STIS CCD by warming the CCD to the ambient instrument
temperature and annealing radiation-damaged pixels.

Radiation damage creates hot pixels in the STIS CCD Detector. Many of
these hot pixels can be repaired by warming the CCD from its normal
operating temperature near -83 deg. C to the ambient instrument
temperature (~ +5 deg. C) for several hours. The number of hot pixels
repaired is a function of annealing temperature. The effectiveness of
the CCD hot pixel annealing process is assessed by measuring the dark
current behavior before and after annealing and by searching for any
window contamination effects.

STIS/CCD 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/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11740

A Complete Optical and NIR Atmospheric Transmission Spectrum of the
Exoplanet

The hot Jupiter HD189733b offers the best exoplanet in which to
perform atmospheric studies through transit spectroscopy. Here we
propose STIS and Nicmos spectra to help construct a full exoplanetary
transit transmission spectrum that extends over the entire optical and
near-infrared range. Such a spectrum will link existing observed
atmospheric features such as haze, water, and methane, providing a
coherent understanding of all these reported features. With a spectrum
covering many observed absorption features, the absolute pressure
scale and abundances can be determined linking observed features to
the actual atmospheric properties of the exoplanet.

WFC3/IR 11738

SPIDERWEBS AND FLIES: OBSERVING MASSIVE GALAXY FORMATION IN ACTION

Distant luminous radio galaxies are among the brightest known galaxies
in the early Universe, pinpoint likely progenitors of dominant cluster
galaxies and are unique laboratories for studying massive galaxy
formation. Spectacular images with the ACS and NICMOS of one such
object, the "Spiderweb Galaxy" at z = 2.2, show in exquisite detail,
hierarchical merging occurring 11 Gyr ago. By imaging 3 additional
Spiderweb-like galaxies we wish to study this potentially crucial
phase of massive galaxy evolution, when hierarchical merging, galaxy
downsizing and AGN feedback are all likely to be occurring. Properties
of the complete sample of Spiderweb galaxies will be used to (i)
constrain models for the formation and evolution of the most massive
galaxies that dominate rich clusters and (ii) investigate the nature
of chain and tadpole galaxies, a fundamental but poorly understood
constituent of the early Universe.

We shall image rest-frame UV and optical continuum emission from 3
radio galaxies with 2.4 z 3.8 that appear clumpy and large in
shallow WFPC/PC observations. The new observations will typically
reach ~2 magnitudes fainter over 20-40 times larger area than
previously. Photometric and morphological parameters will be measured
for satellite galaxies ("flies") in the clumpy massive hosts and for
galaxies in ~ 1.5 Mpc x 1.5 Mpc regions of surrounding protoclusters.
Locations, sizes, elongations, clumpiness, masses, and star formation
rates of the merging satellite and protocluster galaxies will be
compared with new state of the art simulations. Combination of ACS and
WFC3 images will help disentangle the properties of the young and old
populations.

Specific goals include: (i) investigating star formation histories of
the satellite galaxies and the extended emission, (ii) studying
"downsizing" and merging scenarios and (iii) measuring the statistics
of linear galaxies and relating them to models for the formation of
massive galaxies and to the properties of the important but enigmatic
class of chain/tadpole galaxies in the HUDF.

STIS/CCD 11721

Verifying the Utility of Type Ia Supernovae as Cosmological Probes:
Evolution and Dispersion in the Ultraviolet Spectra

The study of distant type Ia supernova (SNe Ia) offers the most
practical and immediate discriminator between popular models of dark
energy. Yet fundamental questions remain over possible
redshift-dependent trends in their observed and intrinsic properties.
High-quality Keck spectroscopy of a representative sample of 36
intermediate redshift SNe Ia has revealed a surprising, and
unexplained, diversity in their rest-frame UV fluxes. One possible
explanation is hitherto undiscovered variations in the progenitor
metallicity. Unfortunately, this result cannot be compared to local UV
data as only two representative SNe Ia have been studied near maximum
light. Taking advantage of two new `rolling searches' and the
restoration of STIS, we propose a non-disruptive TOO campaign to
create an equivalent comparison local sample. This will allow us to
address possible evolution in the mean UV spectrum and its diversity,
an essential precursor to the study of SNe beyond z~1.

WFC3/UVIS 11714

Snapshot Survey for Planetary Nebulae in Local Group Globular Clusters

Planetary nebulae (PNe) in globular clusters (GCs) raise a number of
interesting issues related to stellar and galactic evolution. The
number of PNe known in Milky Way GCs, four, is surprisingly low if one
assumes that all stars pass through a PN stage. However, it is likely
that the remnants of stars now evolving in galactic GCs leave the AGB
so slowly that any ejected nebula dissipates long before the star
becomes hot enough to ionize it. Thus there should not be ANY PNe in
Milky Way GCs--but there are four! It has been suggested that these
Pne are the result of mergers of binary stars within GCs, i.e., that
they are descendants of blue stragglers. The frequency of occurrence
of PNe in external galaxies poses more questions, because it shows a
range of almost an order of magnitude.

I propose a SNAPshot survey aimed at discovering PNe in the GC systems
of Local Group galaxies outside the Milky Way. These clusters, some of
which may be much younger than their counterparts in our galaxy, might
contain many more PNe than those of our own galaxy. I will use the
standard technique of emission-line and continuum imaging, which
easily discloses PNe. This proposal continues a WFPC2 program started
in Cycle 16, but with the more powerful WFC3. As a by-product, the
survey will also produce color-magnitude diagrams for numerous
clusters for the first time, reaching down to the horizontal branch.

STIS/CCD/MA 11668

Cosmo-chronometry and Elemental Abundance Distribution of the Ancient
Star HE1523-0901

We propose to obtain near-UV HST/STIS spectroscopy of the extremely
metal-poor, highly r-process-enhanced halo star HE 1523-0901, in order
to produce the most complete abundance distribution of the heaviest
stable elements, including platinum, osmium, and lead. These HST
abundance data will then be used to estimate the initial abundances of
the long-lived radioactive elements thorium and uranium, and by
comparison with their observed abundances, enable an accurate age
determination of this ancient star. The use of radioactive
chronometers in stars provides an independent lower limit on the age
of the Galaxy, which can be compared with alternative limits set by
globular clusters and by analysis from WMAP. Our proposed observations
of HE1523-0901 will also provide significant new information about the
early chemical history of the Galaxy, specifically, the nature of the
first generations of stars and the types of nucleosynthetic processes
that occurred at the onset of Galactic chemical evolution.

COS/NUV/ACS/WFC/FUV 11658

Probing the Outer Regions of M31 with QSO Absorption Lines

We propose HST-COS spectroscopy of 10 quasars behind M31. Absorption
lines due to MgII, FeII, CIV, and a variety of other lines will be
searched for and measured. Six quasars lie between 1 and 4.2 Holmberg
radii near the major axis on the southwest side, where confusion with
Milky Way gas is minimized. Two lie even farther out on the southwest
side of the major axis. One lies within 1 Holmberg radius. Two of the
10 pass through M31's high velocity clouds seen in a detailed 21 cm
emission map. Exposure time estimates were based on SDSS magnitudes
and available GALEX magnitudes. Thus, using the most well-studied
external spiral galaxy in the sky, our observations will permit us to
check, better than ever before, the standard picture that quasar
metal-line absorption systems such as MgII and CIV arise in an
extended gaseous halo/disk of a galaxy well beyond its observable
optical radius. The observations will yield insights into the nature
of the gas and its connection to the very extended stellar components
of M31 that have recently been studied. Notably the observations have
the potential of extending M31's rotation curve to very large
galactocentric distances, thereby placing new constraints on M31's
dark matter halo.

Finally, we also request that the coordinated parallel orbits be
allocated to this program so that we may image the resolved stellar
content of M31's halo and outer disk.

WFC3/UVIS 11657

The Population of Compact Planetary Nebulae in the Galactic Disk

We propose to secure narrow- and broad-band images of compact
planetary nebulae (PNe) in the Galactic Disk to study the missing link
of the early phases of post-AGB evolution. Ejected AGB envelopes
become PNe when the gas is ionized. PNe expand, and, when large
enough, can be studied in detail from the ground. In the interim, only
the HST capabilities can resolve their size, morphology, and central
stars. Our proposed observations will be the basis for a systematic
study of the onset of morphology. Dust properties of the proposed
targets will be available through approved Spitzer/IRS spectra, and so
will the abundances of the alpha- elements. We will be able thus to
explore the interconnection of morphology, dust grains, stellar
evolution, and populations. The target selection is suitable to
explore the nebular and stellar properties across the galactic disk,
and to set constraints on the galactic evolutionary models through the
analysis of metallicity and population gradients.

STIS/CCD 11626

Searching for the Upper Mass Limit in NGC 3603, the Nearest Giant H II
Region

What is the mass of the highest mass star? 100Mo? 150Mo? 200Mo? Or
higher? Theory gives us little guidance as to what physics sets the
upper mass limit, presuming one exists. Is it due to limitations in
the highest masses that can coalesce? Or is it due to stability issues
in such a behemoth? Observationally, the upper mass limit is poorly
constrained at present, with the strongest evidence coming from the
K-band luminosity function of the Arches cluster near the Galactic
Center. Here we propose to investigate this question by determining
the Initial Mass Function of NGC 3603, the nearest giant H II region.
This cluster is known to contain a wealth of O3 and hydrogen-rich
Wolf-Rayets, the most luminous and massive of stars. By constructing
an accurate H-R diagram for the cluster, we will construct a present
day mass function using newly computed high mass evolutionary tracks,
and convert this to an initial mass function using the inferred ages.
This will allow us to see whether or not there is a true deficit of
high mass stars, evidence of an upper mass cutoff. At the same time we
are likely to establish good masses for the highest mass stars ever
determined. We have laid the groundwork for this project using the
Magellan 6.5-m telescope and the excellent seeing found on Las
Campanas, plus analysis of archival ACS/HRS frames, but we now need to
obtain spectra of the stars unobservable from the ground. This can
only be done with HST and a refurbished STIS.

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.

WFC3/UVIS 11588

Galaxy-Scale Strong Lenses from the CFHTLS Survey

We aim to investigate the origin and evolution of early-type galaxies
using gravitational lensing, modeling the mass profiles of objects
over a wide range of redshifts. The low redshift (z = 0.2) sample is
already in place following the successful HST SLACS survey; we now
propose to build up and analyze a sample of comparable size (~50
systems) at high redshift (0.4 z 0.9) using HST WFC3 Snapshot
observations of lens systems identified by the SL2S collaboration in
the CFHT legacy survey.

WFC3/ACS/IR 11563

Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to
0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields

The first generations of galaxies were assembled around redshifts
z~7-10+, just 500-800 Myr after recombination, in the heart of the
reionization of the universe. We know very little about galaxies in
this period. Despite great effort with HST and other telescopes, less
than ~15 galaxies have been reliably detected so far at z7,
contrasting with the ~1000 galaxies detected to date at z~6, just
200-400 Myr later, near the end of the reionization epoch. WFC3 IR can
dramatically change this situation, enabling derivation of the galaxy
luminosity function and its shape at z~7-8 to well below L*,
measurement of the UV luminosity density at z~7-8 and z~8-9, and
estimates of the contribution of galaxies to reionization at these
epochs, as well as characterization of their properties (sizes,
structure, colors). A quantitative leap in our understanding of early
galaxies, and the timescales of their buildup, requires a total sample
of ~100 galaxies at z~7-8 to ~29 AB mag. We can achieve this with 192
WFC3 IR orbits on three disjoint fields (minimizing cosmic variance):
the HUDF and the two nearby deep fields of the HUDF05. Our program
uses three WFC3 IR filters, and leverages over 600 orbits of existing
ACS data, to identify, with low contamination, a large sample of over
100 objects at z~7-8, a very useful sample of ~23 at z~8-9, and limits
at z~10. By careful placement of the WFC3 IR and parallel ACS
pointings, we also enhance the optical ACS imaging on the HUDF and a
HUDF05 field. We stress (1) the need to go deep, which is paramount to
define L*, the shape, and the slope alpha of the luminosity function
(LF) at these high redshifts; and (2) the far superior performance of
our strategy, compared with the use of strong lensing clusters, in
detecting significant samples of faint z~7-8 galaxies to derive their
luminosity function and UV ionizing flux. Our recent z~7.4 NICMOS
results show that wide-area IR surveys, even of GOODS-like depth,
simply do not reach faint enough at z~7-9 to meet the LF and UV flux
objectives. In the spirit of the HDF and the HUDF, we will waive any
proprietary period, and will also deliver the reduced data to STScI.
The proposed data will provide a Legacy resource of great value for a
wide range of archival science investigations of galaxies at redshifts
z~2- 9. The data are likely to remain the deepest IR/optical images
until JWST is launched, and will provide sources for spectroscopic
follow up by JWST, ALMA and EVLA.

WFC3/UV 11556

Investigations of the Pluto System

We propose a set of high SNR observations of the Pluto system that
will provide improved lightcurves, orbits, and photometric properties
of Nix and Hydra. The key photometric result for Nix and Hydra will be
a vastly improved lightcurve shape and rotation period to test if the
objects are in synchronous rotation or not. A second goal of this
program will be to retrieve a new epoch of albedo map for the surface
of Pluto. These observations will also improve masses and in some case
densities for the bodies in the Pluto system.

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