HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5189
PERIOD
COVERED: 5am September 24 - 5am September 27, 2010 (DOY 267/09:00z-270/09:00z)
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
(None)
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS
GSAcq
24
24
FGS
REAcq
23
23
OBAD
with Maneuver 22
22
SIGNIFICANT
EVENTS: (None)
OBSERVATIONS
SCHEDULED:
COS/NUV/FUV/STIS/CCD
12312
Hubble
Investigation of 103P/Hartley 2 in Support of NASA's DIXI Mission
Comet
103P/Hartley 2 is a small but highly active comet that will pass
unusually
close to the Earth (0.12 AU) during the fall of 2010, when it
will
also be visited by NASA's DIXI spacecraft. We propose a 15-orbit
spectroscopic
observing campaign with Hubble, comprised of three 5-orbit
visits
spanning a 2-month period, to measure the abundances of several
key
volatiles (CO, CO2, S2) and their possible seasonal variations. CO
has
not yet been detected in 103P, and Hubble may be the only facility
capable
of doing it. Hubble is also uniquely capable of providing
confirmation
of DIXI's measurements of the CO2 abundance. The DIXI flyby
is
an exceptional opportunity to study the nature of comets, and Hubble
will
contribute important and unique data to the international campaign
supporting
this mission.
ACS/WFC
12292
SWELLS:
Doubling the Number of Disk-dominated Edge-on Spiral Lens
Galaxies
The
formation of realistic disk galaxies within the LCDM cosmology is
still
largely an unsolved problem. Theory is now beginning to make
predictions
for how dark matter halos respond to galaxy formation, and
for
the properties of disk galaxies. Measuring the density profiles of
dark
matter halos on galaxy scales is therefore a strong test for the
standard
paradigm of galaxy formation, offering great potential for
discovery.
However, the degeneracy between the stellar and dark matter
contributions
to galaxy rotation curves remains a major obstacle. Strong
gravitational
lensing, when combined with spatially resolved kinematics
and
stellar population models, can solve this long-standing problem.
Unfortunately,
this joint methodology could not be exploited until
recently
due to the paucity of known edge-on spiral lenses. We have
developed
and demonstrated an efficient technique to find exactly these
systems.
During supplemental cycle-16 we discovered five new spiral lens
galaxies,
suitable for rotation curve measurements. We propose
multi-color
HST imaging of 16 candidates and 2 partially-imaged
confirmed
systems, to measure a sample of eight new edge-on spiral
lenses.
This program will at least double the number of known
disk-dominated
systems. This is crucial for constraining the relative
contribution
of the disk, bulge and dark halo to the total density
profile.
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.
COS/NUV
12042
COS-GTO:
Pluto
We
seek to measure Pluto's albedo below 2100, to better constrain
surface
composition. COS observations will provide a substantial
improvement
in the S/N of Pluto spectra from <1800 to 2100. Accumulation
of
past HST/FOS spectra yields extremely low S/N below 2000 (S/N of only
1-3
in 100 bins; Krasnopolsky 2001). We expect to achieve S/N=5 at 1950
with
10 binning. In addition to spectrally broad albedo measurements,
these
observations could reveal line or molecular band emission, such as
C
I 1931 or CO 1993.
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.
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/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
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).
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.
FGS
11787
Dynamical
Masses and Radii of Four White Dwarf Stars
This
proposal uses the FGS1R in Trans mode to resolve a pair of double
degenerate
binary systems (WD1639+153 and WD 1818+26) in order to
determine
their orbital elements. In addition, the binaries and several
nearby
field stars are observed by FGS1R in Pos mode to establish the
local
inertial reference frame of each binary, as well as its parallax
and
proper motion. This will allow for a direct measurement of the
distance,
which yields the intrinsic luminosity, and when combined with
the
spectroscopic estimates of the T_eff, the radius of each of the four
WD
stars. When combined with the orbital elements, this leads to a
dynamical
mass measurement for each WD, and a four calibration points of
the
WD mass-radius relation.
ACS/WFC3
11735
The
LSD Project: Dynamics, Merging and Stellar Populations of a Sample
of
Well-Studied LBGs at z~3
A
large observational effort with the ground-based ESO/VLT telescopes
allowed
us to obtain deep, spatially-resolved, near-IR spectra of
complete
sample of 11 Lyman-Break Galaxies at z~3.1. These observations
were
used to obtain, for the first time, the metallicity and the
dynamical
properties of a sample of objects that, albeit small, is
representative
of the total population of the LBGs. We propose to use
HST
to obtain high-resolution optical and near-IR images of this sample
of
LBGs in order to study the broad-band morphology and the stellar
light
distribution of these galaxies. These images, exploiting the
superior
spatial resolution of HST images and the low-background : 1-
will
allow a precise measure of the dynamical mass from the velocity
field
derived with spectroscopy; 2- will permit a comparison of the
distribution
of star formation (from the line emission) with the
underlying
stellar population, and, 3- will be used to check if the
complex
velocity field and the multiple line-emitting regions detected
in
most targets can be ascribed to on-going mergers. This accurate study
will
shed light on a number of unsolved problems still affecting the
knowledge
of the LBGs.
ACS/WFC3
11734
The
Hosts of High Redshift Gamma-Ray Bursts
Gamma-ray
bursts are the most luminous explosive events known, acting as
beacons
to the high redshift universe. Long duration GRBs have their
origin
in the collapse of massive stars and thus select star forming
galaxies
across a wide range of redshift. Due to their bright afterglows
we
can study the details of GRB host galaxies via absorption
spectroscopy,
providing redshifts, column densities and metallicities
for
galaxies far too faint to be accessible directly with current
technology.
We have already obtained deep ground based observations for
many
hosts and here propose ACS/WFC3 and WFC3 observations of the fields
of
bursts at z>3 which are undetected in deep ground based images. These
observations
will study the hosts in emission, providing luminosities
and
morphologies and will enable the construction of a sample of high-z
galaxies
with more detailed physical properties than has ever been
possible
before.
COS/FUV
11619
Definitive
ISM Abundances through Low-mass X-ray Binaries as Lighthouses
We
propose observations of the UV spectra of two low-mass X-ray binaries
(Sco
X-1 and Cyg X-2) with existing Chandra X-Ray Observatory (CXO)
data.
From the X-ray data we will measure total (phase-independent)
column
densities of O, Ne, and Fe. From the UV data we will determine
gas-phase
column densities of H and O. The data in conjunction will
allow
us to make unique measurements of the total interstellar
abundances
of oxygen, neon, and iron, and direct measurements of the
dust-phase
abundances of O and Fe.
WFC3/UV
11605
Obtaining
the Missing Links in the Test of Very Low Mass Evolutionary
Models
with HST
We
are proposing for spatially resolved ACS+HRC observations of 11 very
low
mass binaries spanning late-M, L and T spectral types in order to
obtain
precise effective temperature measurements for each component.
All
of our targets are part of a program in which we are measuring
dynamical
masses of very low-mass binaries to an unprecedented precision
of
10% (or better). However, without precise temperature measurements,
the
full scientific value of these mass measurements cannot be realized.
Together,
mass and temperature measurements will allow us to distinguish
between
brown dwarf evolutionary models that make different assumptions
about
the interior and atmospheric structure of these ultra-cool
objects.
While dynamical masses can be obtained from the ground in the
near-IR,
obtaining precise temperatures require access to optical data
which,
for these sub-arcsecond binaries, can only be obtained from space
with
Hubble.
WFC3/ACS/IR
11600
Star
Formation, Extinction, and Metallicity at 0.7<z<1.5: H-Alpha Fluxes
and
Sizes from a Grism Survey of GOODS-N
The
global star formation rate (SFR) is ~10x higher at z=1 than today.
This
could be due to drastically elevated SFR in some fraction of
galaxies,
such as mergers with central bursts, or a higher SFR across
the
board. Either means that the conditions in z=1 star forming galaxies
could
be quite different from local objects. The next step beyond
measuring
the global SFR is to determine the dependence of SFR,
obscuration,
metallicity, and size of the star-forming region on galaxy
mass
and redshift. However, SFR indicators at z=1 typically apply local
calibrations
for UV, [O II] and far-IR, and do not agree with each other
on
a galaxy-by-galaxy basis. Extinction, metallicity, and dust
properties
cause uncontrolled offsets in SFR calibrations. The great
missing
link is Balmer H-alpha, the most sensitive probe of SFR. We
propose
a slitless WFC3/G141 IR grism survey of GOODS-N, at 2
orbits/pointing.
It will detect Ha+[N II] emission from 0.7<z<1.5, to
L(Ha)
= 1.7 x 10^41 erg/sec at z=1, measuring H-alpha fluxes and sizes
for
> 600 galaxies, and a small number of higher-redshift emitters. This
will
produce: an emission-line redshift survey unbiased by magnitude and
color
selection; star formation rates as a function of galaxy
properties,
e.g. stellar mass and morphology/mergers measured by ACS;
comparisons
of SFRs from H-alpha to UV and far-IR indicators;
calibrations
of line ratios of H-alpha to important nebular lines such
as
[O II] and H-beta, measuring variations in metallicity and extinction
and
their effect on SFR estimates; and the first measurement of scale
lengths
of the H-alpha emitting, star-forming region in a large sample
of
z~1 sources.
ACS/WFC3
11593
Dynamical
Masses of the Coolest Brown Dwarfs
T
dwarfs are excellent laboratories to study the evolution and the
atmospheric
physics of both brown dwarfs and extrasolar planets. To
date,
only a single T dwarf binary has a dynamical mass determination,
and
more are sorely needed. The prospects of measuring more dynamical
masses
over the next decade are limited to 6 known short-period T dwarf
binaries.
We propose here to obtain Long-Term HST/ACS monitoring for the
3
of the 6 binaries which cannot be resolved with AO from the ground.
Upon
completion, our program will substantially increase the number of T
dwarf
dynamical mass measurements and thereby provide key benchmarks for
testing
theoretical models of ultracool objects.
WFC3/IR
11591
Are
Low-Luminosity Galaxies Responsible for Cosmic Reionization?
Our
group has demonstrated that massive clusters, acting as powerful
cosmic
lenses, can constrain the abundance and properties of
low-luminosity
star-forming sources beyond z~6; such sources are thought
to
be responsible for ending cosmic reionization. The large
magnification
possible in the critical regions of well-constrained
clusters
brings sources into view that lie at or beyond the limits of
conventional
exposures such as the UDF. We have shown that the
combination
of HST and Spitzer is particularly effective in delivering
the
physical properties of these distant sources, constraining their
mass,
age and past star formation history. Indirectly, we therefore gain
a
valuable glimpse to yet earlier epochs. Recognizing the result (and
limitations)
of blank field surveys, we propose a systematic search
through
10 lensing clusters with ACS/F814W and WFC3/[F110W+F160W] (in
conjunction
with existing deep IRAC data). Our goal is to measure with
great
accuracy the luminosity function at z~7 over a range of at least 3
magnitude,
based on the identification of about 50 lensed galaxies at
6.5<z<8.
Our survey will mitigate cosmic variance and extend the search
both
to lower luminosities and, by virtue of the WFC3/IRAC combination,
to
higher redshift. Thanks to the lensing amplification spectroscopic
follow-up
will be possible and make our findings the most robust prior
to
the era of JWST and the ELTs.
ACS/SBC/COS/NUV/FUV
11579
The
Difference Between Neutral- and Ionized-Gas Metal Abundances in
Local
Star-Forming Galaxies with COS
The
metallicity of galaxies and its evolution with redshift is of
paramount
importance for understanding galaxy formation. Abundances in
the
interstellar medium (ISM) are typically determined using
emission-line
spectroscopy of HII regions. However, since HII regions
are
associated with recent SF they may not have abundances typical for
the
galaxy as a whole. This is true in particular for star-forming
galaxies
(SFGs), in which the bulk of the metals may be contained in the
neutral
gas. It is therefore important to directly probe the metal
abundances
in the neutral gas. This can be done using absorption lines
in
the Far UV. We have developed techniques to do this in SFGs, where
the
absorption is measured for sightlines toward bright SF regions
within
the galaxy itself. We have successfully applied this technique to
a
sample of galaxies observed with FUSE. The results have been very
promising,
suggesting in I Zw 18 that abundances in the neutral gas may
be
up to 0.5 dex lower than in the ionized gas. However, the
interpretation
of the FUSE data is complicated by the very large FUSE
aperture
(30 arcsec), the modest S/N, and the limited selection of
species
available in the FUSE bandpass. The advent of COS on HST now
allows
a significant advance in all of these areas. We will therefore
obtain
absorption line spectroscopy with G130M in the same sample for
which
we already have crude constraints from FUSE. We will obtain
ACS/SBC
images to select the few optimal sightlines to target in each
galaxy.
The results will be interpreted through line-profile fitting to
determine
the metal abundances constrained by the available lines. The
results
will provide important new insights into the metallicities of
galaxies,
and into outstanding problems at high redshift such as the
observed
offset between the metallicities of Lyman Break Galaxies and
Damped
Lyman Alpha systems.