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Daily Report #5189



 
 
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Old September 27th 10, 05:04 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5189

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 (Z5% solar). There
are almost no X-ray observations of such low abundance galaxies (3 in
the Chandra archive). These are the most metal-deficient galaxies
known, and a logical place to find ULX if they favor metal-poor
systems. We plan to test recent population synthesis models which
predict that ULX should be very numerous in metal-poor galaxies. We
will also test the hypothesis that ULX form in massive young star
clusters, and ask for HST time to obtain the necessary imaging data.

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 z3 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 0.7z1.5: 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 0.7z1.5, 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 6.5z8. 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.


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