Status Report

NASA Hubble Space Telescope Daily Report # 3496

By SpaceRef Editor
November 25, 2003
Filed under , ,





ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground mass
provide a powerful method of directly measuring the amount and distribution of
dark matter. Several groups have recently detected this weak lensing by
large-scale structure, also called cosmic shear. The high resolution and
sensitivity of HST/ACS provide a unique opportunity to measure cosmic shear
accurately on small scales. Using 260 parallel orbits in Sloan textiti {F775W}
we will measure for the first time: beginlistosetlength sep0cm
setlength opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the
skewness of the shear distribution, and em the magnification effect.
endlist Our
measurements will determine the amplitude of the mass power spectrum
sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass density
Omega_m with s/n=4. They will be done at small angular scales where non-linear
effects dominate the power spectrum, providing a test of the gravitational
instability paradigm for structure formation. Measurements on these scales are
not possible from the ground, because of the systematic effects induced by PSF
smearing from seeing. Having many independent lines of sight reduces the
uncertainty due to cosmic variance, making parallel observations ideal.

ACS/HRC 10050

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth with the
HRC and WFC. These observations will be used to verify the accuracy of the
currently used by the pipeline and will provide a comparison with flats derived
via other techniques: L-flats from stellar observations, sky flats from stacked
GO observations, and internal flats using the calibration lamps. Weekly
coronographic monitoring is required to assess the changing position of the


CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
of hot pixels and test for any source of noise in ACS CCD detectors. This
programme will be executed once a day for the entire lifetime of ACS.


Elliptical galaxies in z~1.5 clusters

Giant elliptical galaxies offer can some of the tightest constraints on models
of galaxy formation. Recent observations have shown significant inconsistencies
between their properties and the predictions of the currently popular
hierarchical clustering models. Many outstanding questions about the nature and
evolution of these objects can best {or only} be addressed by extending studies
of cluster ellipticals out to z>1. Recently we have identified large
overdensities of red galaxies, strongly clustered around powerful radio sources
at z~1.5. We propose to image our two richest fields, of Abell Class 0-1
richness, using the F814W and F606W filters on the ACS/WFC. Our goals are to
investigate: {1} Galaxy morphologies: we will determine the bulge fractions of
the red cluster galaxies, to confirm that they are early-types, and measure
their characteristic radii to investigate their evolutionary status. {2} Colour
gradients: we will search for colour gradients indicative of recent star
formation {particularly blue cores}, or inhomogeneities in the internal colours
which might be indicative of recent assembly. {3} Cluster membership: with two
additional colours we will obtain accurate photometric redshift estimates for
all galaxies. Combined with studies of nearby clusters and of field
our results will place very tight constraints on the formation of the most
massive galaxies.

FGS 9329

The Masses and Luminosities of Population II Stars

Very little is currently known concerning the mass-luminosity relation {MLR} of
Population II stars. However, with the advent of the Hipparcos Catalogue,
improved distances to many spectroscopic binaries known to be Pop II
systems are
now available. After surveying the literature and making reasonable
estimates of
the secondary masses, we find 13 systems whose minimum separation should be
larger than the resolution limit of FGS1. Because of the expected magnitude
differences and separations, it is not possible to resolve the systems from the
ground. We therefore propose FGS observations of the sample. In combination
the known spectroscopic orbits and Hipparcos distances, these observations will
yield up to 26 precise stellar mass determinations of metal-poor stars, if all
systems are resolved and the relative orbits are determined. A combination of
FGS data and ground-based observations will lead to component luminosities and
effective temperatures. This program will allow for a significantly better
understanding of the Pop II main sequence, which in turn will lead to better
ages and distances of the galactic globular clusters, and a Pop II MLR will be
constructed for the first time.

NIC/NIC3 9865

The NICMOS Parallel Observing Program

We propose to continue managing the NICMOS pure parallel program. Based on our
experience, we are well prepared to make optimal use of the parallel
opportunities. The improved sensitivity and efficiency of our observations will
substantially increase the number of line-emitting galaxies detected. As our
previous work has demonstrated, the most frequently detected line is Halpha at
0.7<z<1.9, which provides an excellent measure of current star formation rate.
We will also detect star-forming and active galaxies in other redshift ranges
using other emission lines. The grism observations will produce by far the best
available Halpha luminosity functions over the crucial–but poorly
observed–redshift range where galaxies appear to have assembled most of their
stellar mass. This key process of galaxy evolution needs to be studied with IR
data; we found that observations at shorter wavelengths appear to have missed a
large fraction of the star-formation in galaxies, due to dust reddening. We
also obtain deep F110W and F160W images, to examine the space densities and
morphologies of faint red galaxies. In addition to carrying out the public
parallels, we will make the fully reduced and calibrated images and spectra
available on-line, with some ground-based data for the deepest parallel fields


NICMOS Post-SAA calibration – CR Persistence Part 1.

A new procedure proposed to alleviate the CR-persistence problem of NICMOS.
frames will be obtained immediately upon exiting the SAA contour 23, and every
time a NICMOS exposure is scheduled within 50 minutes of coming out of the SAA.
The darks will be obtained in parallel in all three NICMOS Cameras. The
darks will be non-standard reference files available to users with a USEAFTER
date/time mark.

STIS/CCD 10017

CCD Dark Monitor-Part 1

Monitor the darks for the STIS CCD.

STIS/CCD 10019

CCD Bias Monitor – Part 1

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1
at gain = 4, to build up high-S/N superbiases and track the evolution of hot

STIS/CCD 10022

STIS CCD Hot Pixel Annealing Cycle 12

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. In addition CTE performance is
examined by
looking for traps in a low signal level flat. Follows on from proposal 9612.

STIS/CCD/MA1 10081

Is the exoplanet HD209458b’s exosphere in a blowoff state ?

Using HST Lyman alpha observations, we have detected an extended tail shaped
upper atmosphere around the extra-solar planet HD209458b. The Cycle 10 STIS
G140M observations revealed an absorption of 15+/-4% of the stellar Lyman alpha
emission line during the planetary transit in front of the star {Vidal-Madjar,
et al. 2003}. This showed that HI evaporation is taking place within a highly
extended upper atmosphere. Very recent studies on the evaporation mechanism are
now indicating that instead of “Jeans escape” a more probable mechanism is
complete atmospheric “blowoff” as suffered by the telluric planets in the
early solar system. This mecanism could be directly tested with HST by
for the escape of species slightly heavier than HI. It is easy to show that
neither oxygen nor carbon would be detected with HST if only “Jeans escape”
takes place while both species, under “blowoff” conditions, should reach the
Roche limit of the planet and escape as hydrogen. If this is the case an
absorption during transit of about 15% should be observed for both. Twelve
orbits with the STIS G140L spectrograph will allow us to detect the presence of
these species during three transits with a better than 5% accuracy, needed to
detect an object of the size of the planetary Roche lobe. Simultaneously these
observations will confirm and give more precision about the extention of the HI
cometary like tail expected to occult the star well after the end of the
transit. This proposed investigation is a unique opportunity to further study
hot giant planets upper atmospheres, reveal the precise evaporation mechanism
and give new constraints on the “hot Jupiters” lifetime. This could explain
the lack of planets discovered so far at less than 0.04~AU from their star. We
ask for HST observations under Director Discretionnary time to have access to
the coming transits observable in the early fall of 2003.


Confirmation of New Candidates for the Study of Intergalactic Helium

The reionization of intergalactic helium is believed to take place between
redshift 3 and 4. The study of HeII Lyman-alpha absorption in four quasars at
2.7<z<3.3 demonstrates the great potential of such an intergalactic-medium
probe and suggests that the reionization epoch is at higher redshifts. Clean
quasar sightlines may be found only from massive pre-selection processes in the
optical and UV, because of random, severe absorption by intervening Lyman-limit
systems. The SDSS has discovered approximately 36000 quasars, and we propose to
verify the UV detectability in 70 top candidates for helium studies
extending to
even higher redshift. Our proposed approach has already proven successful, and
additional positive confirmations will allow follow-up observations, with STIS
or COS, to pinpoint the epoch of reionization of the IGM, and the evolution of
its properties near that period.

WFPC2 10068

WFPC2 CYCLE 12 Standard Darks

This dark calibration program obtains dark frames every week in order to
data for the ongoing calibration of the CCD dark current rate, and to monitor
and characterize the evolution of hot pixels. Over an extended period these
will also provide a monitor of radiation damage to the CCDs.

WFPC2 10069

WFPC2 CYCLE 12 Supplemental Darks, Part 1/3

This dark calibration program obtains 3 dark frames every day to provide data
for monitoring and characterizing the evolution of hot pixels.

WFPC2 10072


This calibration proposal is the Cycle 12 routine internal monitor for
WFPC2, to
be run weekly to monitor the health of the cameras. A variety of internal
exposures are obtained in order to provide a monitor of the integrity of
the CCD
camera electronics in both bays {gain 7 and gain 15}, a test for quantum
efficiency in the CCDs, and a monitor for possible buildup of contaminants on
the CCD windows.

WFPC2 10075

WFPC2 CYCLE 12 Intflat and Viflat Sweeps and Filter Rotation Anomaly Monitor

Using intflat observations, this WFPC2 proposal is designed to monitor the
pixel-to-pixel flatfield response and provide a linearity check. The intflat
sequences, to be done once during the year, are similar to those from the Cycle
11 program 9597. The images will provide a backup database in the event of
complete failure of the visflat lamp as well as allow monitoring of the gain
ratios. The sweep is a complete set of internal flats, cycling through both
shutter blades and both gains. The linearity test consists of a series of
intflats in F555W, in each gain and each shutter. As in Cycle 11, we plan to
continue to take extra visflat, intflat, and earthflat exposures to test the
repeatability of filter wheel motions.

WFPC2 10082

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans

WFPC2 9709

POMS Test Proposal: WFII parallel archive proposal

This is the generic target version of the WFPC2 Archival Pure Parallel program.
The program will be used to take parallel images of random areas of the sky,
following the recommendations of the 2002 Parallels Working Group.


Significant Spacecraft Anomalies: (The following are preliminary reports of
potential non-nominal performance that will be investigated.) None



                        SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq            08                        08
FGS REacq            13                        13
FHST Update          12                        12


Autonomous FGS ITS on-board testing (Proposal 04974) FGS 1 @ 329/12:30Z –
(Visit 11) and FGS 3 @ 329/12:48Z – 12:56Z (Visit 12).

SpaceRef staff editor.