HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5018
PERIOD
COVERED: 5am January 22 - 5am January 25, 2010 (DOY 022/10:00z-025/10:00z)
OBSERVATIONS
SCHEDULED
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
11916
IR
Intrapixel Sensitivity
In
order to characterize the periodic intrapixel sensitivity variation
(IPSV)
of the WFC3 IR array, we will analyze full-frame IR observations
of
a star field (in the Omega Centauri globular cluster) in three
bandpasses
(F110W, F160W, and F098M) dithered on an NxN grid. The
measurements
will be used to quantify systematic trends in aperture
photometry
of stars with pixel phase, defined as (x mod 1, y mod 1),
where
(x, y) is the center of the stellar image at subpixel precision.
Grid
sizes of N=2 and N=3 are justifed in Additional Comments of
Proposal
Description.
WFC3/IR
11915
IR
Internal Flat Fields
This
program is the same as 11433 (SMOV) and depends on the completion
of
the IR initial alignment (Program 11425). This version contains three
instances
of 37 internal orbits: to be scheduled early, middle, and near
the
end of Cycle 17, in order to use the entire 110-orbit allocation.
In
this test, we will study the stability and structure of the IR
channel
flat field images through all filter elements in the WFC3-IR
channel.
Flats will be monitored, i.e. to capture any temporal trends in
the
flat fields and delta flats produced. High signal observations will
provide
a map of the pixel-to- pixel flat field structure, as well as
identify
the positions of any dust particles.
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).
ACS/WFC3
11882
CCD
Hot Pixel Annealing
All
the data for this program is acquired using internal targets (lamps)
only,
so all of the exposures should be taken during Earth occultation
time
(but not during SAA passages). 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.
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). The High Resolution Channel (HRC) visits have been
removed
since it could not be repaired during SM4.
ACS/WFC3
11879
CCD
Daily Monitor (Part 1)
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 352 orbits (22 weeks) from 31 August 2009 to 31 January
2010.
STIS/MA1/MA2
11857
STIS
Cycle 17 MAMA Dark Monitor
This
proposal monitors the behavior of the dark current in each of the
MAMA
detectors.
The
basic monitor takes two 1380s ACCUM darks each week with each
detector.
However, starting Oct 5, pairs are only included for weeks
that
the LRP has external MAMA observations planned. The weekly pairs of
exposures
for each detector are linked so that they are taken at
opposite
ends of the same SAA free interval. This pairing of exposures
will
make it easier to separate long and short term temporal variability
from
temperature dependent changes.
For
both detectors, additional blocks of exposures are taken once every
six
months. These are groups of five 1314s FUV-MAMA Time-Tag darks or
five
3x315s NUV ACCUM darks distributed over a single SAA-free interval.
This
will give more information on the brightness of the FUV MAMA dark
current
as a function of the amount of time that the HV has been on, and
for
the NUV MAMA will give a better measure of the short term
temperature
dependence.
STIS/CCD
11846
CCD
Bias Monitor-Part 1
The
purpose of this proposal is to 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
11844
CCD
Dark Monitor Part 1
The
purpose of this proposal is to monitor the darks for the STIS CCD.
STIS/CCD/MA1/MA2
11839
The
Cycles of Alpha Centauri
This
is the HST part of a joint Chandra/HST observing program. The
objective
of the HST part is to obtain new UV spectra of both components
of
the Alpha Centauri binary: the primary ("Alpha Cen A") is a near twin
of
the Sun, while the companion ("B") is an early K dwarf, slightly less
massive,
smaller and less luminous than the Sun. The orbital period is
80
yr, and the two stars currently are separated by about 8". The Alpha
Cen
system has been the subject of long term coronal X-ray monitoring by
four
successive generations of space observatories, and extensive UV
measurements
were obtained periodically during the IUE era, from the
late
1970's to late 1990's. The present program will obtain new STIS
echelle
spectra of both stars, which each were observed in selected
wavelength
windows by GHRS in the mid-1990's, and Alpha Cen A later by
STIS
in an extensive high-res program in 1999, although B unfortunately
never
was recorded by STIS.
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/ACS/UVIS
11724
Direct
Age Determination of the Local Group dE Galaxies NGC 147 and NGC
185
The
origin of dwarf elliptical (dE) galaxies remains a mystery and the
dE
galaxies of the Local Group provide the best opportunity to study
this
galaxy class in detail. We propose to obtain ACS photometry of
main
sequence turnoff stars in the M31 dE satellites NGC 147 and NGC
185.
Because these galaxies have little to no stars younger than 1 Gyr,
resolving
the main sequence turnoff is required to directly quantify
their
star formation histories. NGC 147 and NGC 185 are the only two dEs
for
which a clean measurement is feasible with the HST. This proposal
was
accepted in Cycle 15, but little data were taken before the failure
of
ACS. The main sequence turnoffs of NGC 147 and NGC 185 are expected
to
be at an apparent magnitude of V=29; we request F606W/F814W imaging
one
half magnitude fainter than this limit (three magnitudes fainter
than
the deepest previous dE observations). Quantifying the ratio of old
to
intermediate-age stars will allow us to discriminate between
competing
models of dE formation. On-going Keck/DEIMOS spectroscopy of
several
hundred red giant stars in each of these two dE galaxies,
coupled
with dynamical modeling and spectral synthesis, will complement
the
ACS measurement by providing information on chemical abundance
patterns,
dark matter content and internal dynamics. The proposed ACS
data
will be the first to directly quantify the onset and duration of
star
formation episodes in dE galaxies, and will thereby form the
cornerstone
in what promises to be the most comprehensive study of this
class
of galaxies.
WFC3/ACS/IR
11677
Is
47 Tuc Young? Measuring its White Dwarf Cooling Age and Completing a
Hubble
Legacy
With
this proposal we will firmly establish the age of 47 Tuc from its
cooling
white dwarfs. 47 Tuc is the nearest and least reddened of the
metal-rich
disk globular clusters. It is also the template used for
studying
the giant branches of nearby resolved galaxies. In addition,
the
age sensitive magnitude spread between the main sequence turnoff and
horizontal
branch is identical for 47 Tuc, two bulge globular clusters
and
the bulge field population. A precise relative age constraint for 47
Tuc,
compared to the halo clusters M4 and NGC 6397, both of which we
recently
dated via white dwarf cooling, would therefore constrain when
the
bulge formed relative to the old halo globular clusters. Of
particular
interest is that with the higher quality ACS data on NGC
6397,
we are now capable with the technique of white dwarf cooling of
determining
ages to an accuracy of +/-0.4 Gyrs at the 95% confidence
level.
Ages derived from the cluster turnoff are not currently capable
of
reaching this precision. The important role that 47 Tuc plays in
galaxy
formation studies, and as the metal-rich template for the
globular
clusters, makes the case for a white dwarf cooling age for this
metal-rich
cluster compelling.
Several
recent analyses have suggested that 47 Tuc is more than 2 Gyrs
younger
than the Galactic halo. Others have suggested an age similar to
that
of the most metal poor globular clusters. The current situation is
clearly
uncertain and obviously a new approach to age dating this
important
cluster is required.
With
the observations of 47 Tuc, this project will complete a legacy for
HST.
It will be the third globular cluster observed for white dwarf
cooling;
the three covering almost the full metallicity range of the
cluster
system. Unless JWST has its proposed bluer filters (700 and 900
nm)
this science will not be possible perhaps for decades until a large
optical
telescope is again in space. Ages for globular clusters from the
main
sequence turnoff are less precise than those from white dwarf
cooling
making the science with the current proposal truly urgent.
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.
WFC3/UVIS/IR
11644
A
Dynamical-Compositional Survey of the Kuiper Belt: A New Window Into
the
Formation of the Outer Solar System
The
eight planets overwhelmingly dominate the solar system by mass, but
their
small numbers, coupled with their stochastic pasts, make it
impossible
to construct a unique formation history from the dynamical or
compositional
characteristics of them alone. In contrast, the huge
numbers
of small bodies scattered throughout and even beyond the
planets,
while insignificant by mass, provide an almost unlimited number
of
probes of the statistical conditions, history, and interactions in
the
solar system. To date, attempts to understand the formation and
evolution
of the Kuiper Belt have largely been dynamical simulations
where
a hypothesized starting condition is evolved under the
gravitational
influence of the early giant planets and an attempt is
made
to reproduce the current observed populations. With little
compositional
information known for the real Kuiper Belt, the test
particles
in the simulation are free to have any formation location and
history
as long as they end at the correct point. Allowing compositional
information
to guide and constrain the formation, thermal, and
collisional
histories of these objects would add an entire new dimension
to
our understanding of the evolution of the outer solar system. While
ground
based compositional studies have hit their flux limits already
with
only a few objects sampled, we propose to exploit the new
capabilities
of WFC3 to perform the first ever large-scale
dynamical-compositional
study of Kuiper Belt Objects (KBOs) and their
progeny
to study the chemical, dynamical, and collisional history of the
region
of the giant planets. The sensitivity of the WFC3 observations
will
allow us to go up to two magnitudes deeper than our ground based
studies,
allowing us the capability of optimally selecting a target list
for
a large survey rather than simply taking the few objects that can be
measured,
as we have had to do to date. We have carefully constructed a
sample
of 120 objects which provides both overall breadth, for a general
understanding
of these objects, plus a large enough number of objects in
the
individual dynamical subclass to allow detailed comparison between
and
within these groups. These objects will likely define the core
Kuiper
Belt compositional sample for years to come. While we have many
specific
results anticipated to come from this survey, as with any
project
where the field is rich, our current knowledge level is low, and
a
new instrument suddenly appears which can exploit vastly larger
segments
of the population, the potential for discovery -- both
anticipated
and not -- is extraordinary.
WFC3/IR
11631
Binary
Brown Dwarfs and the L/T Transition
Brown
dwarfs traverse spectral types M, L and T as their atmospheric
structure
evolves and they cool into oblivion. This SNAPSHOT program
will
obtain WFC3-IR images of 45 nearby late-L and early-T dwarfs to
investigate
the nature of the L/T transition. Recent analyses have
suggested
that a substantial proportion of late-L and early-T dwarfs are
binaries,
comprised of an L dwarf primary and T dwarf secondary. WFC3-IR
observations
will let us quantify this suggestion by expanding coverage
to
a much larger sample, and permitting comparison of the L/T binary
fraction
against ‘normal’ ultracool dwarfs. Only eight L/T binaries are
currently
known, including several that are poorly resolved: we
anticipate
at least doubling the number of resolved systems. The
photometric
characteristics of additional resolved systems will be
crucial
to constraining theoretical models of these late-type ultracool
dwarfs.
Finally, our data will also be eminently suited to searching for
extremely
low luminosity companions, potentially even reaching the Y
dwarf
regime.
STIS/CCD/MA1/MA2
11616
The
Disks, Accretion, and Outflows (DAO) of T Tau Stars
Classical
T Tauri stars undergo magnetospheric accretion, power
outflows,
and possess the physical and chemical conditions in their
disks
to give rise to planet formation. Existing high resolution FUV
spectra
verify that this spectral region offers unique diagnostics of
these
processes, which have the potential to significantly advance our
understanding
of the interaction of a star and its accretion disk. To
date
the limited results are intriguing, with dramatic differences in
kinematic
structure in lines ranging from C IV to H2 among the few stars
that
have been observed. We propose to use HST/COS to survey the disks,
outflows,
and accretion (the DAO) of 26 CTTS and 6 WTTS in the FUV at
high
spectral resolution. A survey of this size is essential to
establish
how properties of accretion shocks, winds and disk irradiation
depend
on disk accretion rate. Specifically, our goals are to (1)
measure
the radiation from and understand the physical properties of the
gas
very near the accretion shock as a function of accretion rate using
emission
line profiles of hot lines (C IV, Si IV, N V, and He II); (2)
measure
the opacity, velocity, and temperature at the base of the
outflow
to constrain outflow models using wind absorption features; and
(3)
characterize the radiation incident on disks and protoplanetary
atmospheres
using H2 line and continuum emission and reconstructed
bright
Ly-alpha line emission.
WFC3/ACS/UVIS
11613
GHOSTS:
Stellar Outskirts of Massive Spiral Galaxies
We
propose to continue our highly successful GHOSTS HST survey of the
resolved
stellar populations of nearby, massive disk galaxies using
SNAPs.
These observations provide star counts and color-magnitude
diagrams
2-3 magnitudes below the tip of the Red Giant Branch of the
outer
disk and halo of each galaxy. We will measure the metallicity
distribution
functions and stellar density profiles from star counts
down
to very low average surface brightnesses, equivalent to ~32 V-mag
per
square arcsec.
This
proposal will substantially improve our unique sampling of galaxy
outskirts.
Our targets cover a range in galaxy mass, luminosity,
inclination,
and morphology. As a function of these galaxy properties,
this
survey provides: - the most extensive, systematic measurement of
radial
light profiles and axial ratios of the diffuse stellar halos and
outer
disks of spiral galaxies; - a comprehensive analysis of halo
metallicity
distributions as function of galaxy type and position within
the
galaxy; - an unprecedented study of the stellar metallicity and age
distribution
in the outer disk regions where the disk truncations occur;
-
the first comparative study of globular clusters and their field
stellar
populations.
We
will use these fossil records of the galaxy assembly process to test
halo
formation models within the hierarchical galaxy formation scheme.
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
11577
Opening
New Windows on the Antennae with WFC3
We
propose to use WFC3 to provide key observations of young star
clusters
in "The Antennae" (NGC4038/39). Of prime importance is the
WFC3's
ability to push the limiting UV magnitude FIVE mag deeper than
our
previous WFPC2 observations. This corresponds to pushing the
limiting
cluster mass from ~10**5 to ~10**3 solar masses for cluster
ages
~10**8 yrs. In addition, the much wider field of view of the WFC3
IR
channel will allow us to map out both colliding disks rather than
just
the Overlap Region between them. This will be especially important
for
finding the youngest clusters that are still embedded in their
placental
cocoons. The extensive set of narrow- band filters will
provide
an effective means for determining the properties of shocks,
which
are believed to be a primary triggering mechanism for star
formation.
We will also use ACS in parallel with WFC3 to observe
portions
of both the northern and southern tails at no additional
orbital
cost. Finally, one additional primary WFC3 orbit will be used to
supplement
exisiting HST observations of the star-forming "dwarf" galaxy
at
the end of the southern tail. Hence, when completed we will have full
UBVI
+ H_alpha coverage (or more for the main galaxy) of four different
environments
in the Antennae. In conjunction with the extensive
multi-wavelength
database we have collected (both HST and ground based)
these
observations will provide answers to fundamental questions such
as:
How do these clusters form and evolve? How is star formation
triggered?
How do star clusters affect the local and global ISM, and the
evolution
of the galaxy as a whole? The Antennae galaxies are the
nearest
example of a major disk--disk merger, and hence may represent
our
best chance for understanding how mergers form tremendous numbers of
clusters
and stars, both in the local universe and during galaxy
assembly
at high redshift.
WFC3/ACS/UVIS/IR
11570
Narrowing
in on the Hubble Constant and Dark Energy
A
measurement of the Hubble constant to a precision of a few percent
would
be a powerful aid to the investigation of the nature of dark
energy
and a potent "end-to end" test of the present cosmological model.
In
Cycle 15 we constructed a new streamlined distance ladder utilizing
high-
quality type Ia supernova data and observations of Cepheids with
HST
in the near-IR to minimize the dominant sources of systematic
uncertainty
in past measurements of the Hubble constant and reduce its
total
uncertainty to a little under 5%. Here we propose to exploit this
new
route to reduce the remaining uncertainty by more than 30%,
translating
into an equal reduction in the uncertainty of the equation
of
state of dark energy. We propose three sets of observations to reach
this
goal: a mosaic of NGC 4258 with WFC3 in F160W to triple its sample
of
long period Cepheids, WFC3/F160W observations of the 6 ideal SN Ia
hosts
to triple their samples of Cepheids, and observations of NGC 5584
the
host of a new SN Ia, SN 2007af, to discover and measure its Cepheids
and
begin expanding the small set of SN Ia luminosity calibrations.
These
observations would provide the bulk of a coordinated program aimed
at
making the measurement of the Hubble constant one of the leading
constraints
on dark energy.
STIS/CCD/MA2
11568
A
SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations
of
Stars with Archived FUV Observations
We
propose to obtain high-resolution STIS E230H SNAP observations of
MgII
and FeII interstellar absorption lines toward stars within 100
parsecs
that already have moderate or high-resolution far- UV (FUV),
900-1700
A, observations available in the MAST Archive. Fundamental
properties,
such as temperature, turbulence, ionization, abundances, and
depletions
of gas in the local interstellar medium (LISM) can be
measured
by coupling such observations. Due to the wide spectral range
of
STIS, observations to study nearby stars also contain important data
about
the LISM embedded within their spectra. However, unlocking this
information
from the intrinsically broad and often saturated FUV
absorption
lines of low-mass ions, (DI, CII, NI, OI), requires first
understanding
the kinematic structure of the gas along the line of
sight.
This can be achieved with high resolution spectra of high-mass
ions,
(FeII, MgII), which have narrow absorption lines, and can resolve
each
individual velocity component (interstellar cloud). By obtaining
short
(~10 minute) E230H observations of FeII and MgII, for stars that
already
have moderate or high-resolution FUV spectra, we can increase
the
sample of LISM measurements, and thereby expand our knowledge of the
physical
properties of the gas in our galactic neighborhood. STIS is the
only
instrument capable of obtaining the required high resolution data
now
or in the foreseeable future.
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.
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 followup by
JWST,
ALMA and EVLA.
WFC3/ACS/IR
11235
HST
NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies
in
the Local Universe
At
luminosities above 10^11.4 L_sun, the space density of far-infrared
selected
galaxies exceeds that of optically selected galaxies. These
`luminous
infrared galaxies' (LIRGs) are primarily interacting or
merging
disk galaxies undergoing enhanced star formation and Active
Galactic
Nuclei (AGN) activity, possibly triggered as the objects
transform
into massive S0 and elliptical merger remnants. We propose
NICMOS
NIC2 imaging of the nuclear regions of a complete sample of 88
L_IR
> 10^11.4 L_sun luminous infrared galaxies in the IRAS Revised
Bright
Galaxy Sample (RBGS: i.e., 60 micron flux density > 5.24 Jy).
This
sample is ideal not only in its completeness and sample size, but
also
in the proximity and brightness of the galaxies. The superb
sensitivity
and resolution of NICMOS NIC2 on HST enables a unique
opportunity
to study the detailed structure of the nuclear regions,
where
dust obscuration may mask star clusters, AGN, and additional
nuclei
from optical view, with a resolution significantly higher than
possible
with Spitzer IRAC. This survey thus provides a crucial
component
to our study of the dynamics and evolution of IR galaxies
presently
underway with Wide-Field, HST ACS/WFC3, and Spitzer IRAC
observations
of these 88 galaxies. Imaging will be done with the F160W
filter
(H-band) to examine as a function of both luminosity and merger
stage:
(i) the luminosity and distribution of embedded star clusters,
(ii)
the presence of optically obscured AGN and nuclei, (iii) the
correlation
between the distribution of 1.6 micron emission and the
mid-IR
emission as detected by Spitzer IRAC, (iv) the evidence of bars
or
bridges that may funnel fuel into the nuclear region, and (v) the
ages
of star clusters for which photometry is available via ACS/WFC3
observations.
The NICMOS data, combined with the HST ACS, Spitzer, and
GALEX
observations of this sample, will result in the most comprehensive
study
of merging and interacting galaxies to date.
WFC3/IR
11189
Probing
the Early Universe with GRBs
Cosmology
is beginning to constrain the nature of the earliest stars and
galaxies
to form in the Universe, but direct observation of galaxies at
z>6
remains highly challenging due to their scarcity, intrinsically
small
size, and high luminosity distance. GRB afterglows, thanks to
their
extreme luminosities, offer the possibility of circumventing these
normal
constraints by providing redshifts and spectral information which
couldn't
be obtained through direct observation of the host galaxies
themselves.
In addition, the association of GRBs with massive stars
means
that they are an indicator of star formation, and that their hosts
are
likely responsible for a large proportion of the ionizing radiation
during
that era. Our collaboration is conducting a campaign to rapidly
identify
and study candidate very high redshift bursts, bringing to bear
a
network of 2, 4 and 8m telescopes with near-IR instrumentation. Swift
has
proven capable of detecting faint, distant GRBs, and reporting
accurate
positions for many bursts in near real-time. Here we propose to
continue
our HST program of targeting GRBs at z~6 and above. HST is
crucial
to this endeavor, allowing us (a) to characterize the basic
properties,
such as luminosity and color, and in some cases
morphologies,
of the hosts, which is essential to understanding these
primordial
galaxies and their relationship to other galaxy populations;
and
(b) to monitor the late time afterglows and hence compare them to
lower-z
bursts and test the use of GRBs as standard candles.
NIC3/WFC3/IR
11153
The
Physical Nature and Age of Lyman Alpha Galaxies
In
the simplest scenario, strong Lyman alpha emission from high redshift
galaxies
would indicate that stellar populations younger than 10 Myrs
dominate
the UV. This does not, however, constrain the stellar
populations
older than 100 Myrs, which do not contribute to UV light.
Also,
the Lyman alpha line can be boosted if the interstellar medium is
both
clumpy and dusty. Different studies with small samples have reached
different
conclusions about the presence of dust and old stellar
populations
in Lyman alpha emitters. We propose HST-NICMOS and
Spitzer-IRAC
photometry of 35 Lyman-alpha galaxies at redshift
4.5<z<6.5,
in order to determine their spectral energy distribution
(SED)
extending through rest-frame optical. This will allow us to
measure
accurately (1) The total stellar mass in these objects,
including
old stars which may have formed at redshifts (z > 8) not
easily
probed by any other means. (2) The dust extinction in the
rest-frame
UV, and therefore a correction to their present
star-formation
rates. Taken together, these two quantities will yield
the
star-formation histories of Lyman alpha galaxies, which form fully
half
of the known galaxies at z=4-6. They will tell us whether these are
young
or old galaxies by straddling the 4000A break. Data from NICMOS is
essential
for these compact and faint (i=25-26th magnitude AB) high
redshift
galaxies, which are too faint for good near-IR photometry from
the
ground.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
12172
- GSAcq(2,1,1) at 15:04:28, REAca(2,1,1) at 16:32:37 and REAcq(2,1,1) at
18:08:30
failed to RGA control with Search Radius Limit exceeded on
FGS.
Observations affected: WFC3 185 - 193; Proposal ID# 11570.
12173
- GSAcq(2,1,1) at 024/21:51:07 and REAcq(2,1,1) at 22:50:03 acquired in fine
lock
backup on FGS 2.
Observations possibly affected: WFC3 231 - 235, 002;
Proposal ID# 11631, 11908.
COMPLETED
OPS REQUEST:
18802-0
- Null genslew for proposal 12053 - Slot 1 @ 023/1000z
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
20
19
FGS
REAcq
30
28
OBAD
with Maneuver 13
13
SIGNIFICANT
EVENTS: (None)