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 (Z<5% 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 z>7, 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.