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Daily # 4194



 
 
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Old September 8th 06, 02:54 PM posted to sci.astro.hubble
Joe Cooper
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Default Daily # 4194

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4194

PERIOD COVERED: UT September 07, 2006 (DOY 250)

OBSERVATIONS SCHEDULED

ACS/HRC 10563

Accurate dark-matter mass profiles in 3 elliptical galaxies as a test
of CDM

A critical test of the successful Lambda-CDM picture for structure
formation is the measurement of the power law exponent, gamma, of the
centre of dark matter density profiles, predicted to lie in the range
1.0-1.5. Measurements of gamma derived from rotation curves of LSB
galaxies appear to contradict CDM, but rely on assumptions that are
difficult to verify {e.g. axisymmetry}. We have recently demonstrated,
using our new `semi-linear' inversion method, how strong gravitational
lensing by galaxies can provide a clean and accurate measurement of
gamma, free of such ambiguities. HST images of lensed non-AGN galaxies
provide hundreds of resolution elements, each a constraint on the mass
profile. Such lenses are exceedingly rare, but we have recently
discovered new systems. We propose deep ACS-HRC observations of 3
systems to measure gamma in each, accurate to 0.15 {95% confidence}
and to obtain an indication of its variation between galaxies. To
establish the required number of orbits we have undertaken an
end-to-end simulation of the problem, creating and analysing synthetic
ACS images. Additionally the semi-linear method simultaneously
reconstructs the pixelised source surface brightness distribution. Our
simulations demonstrate that the fine sampling and small pixel
scattering of the HRC, resolves the morphology of the sources with
exquisite detail.

ACS/HRC 10800

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the
early dynamical evolution of the outer Solar System. We propose to
continue a Snapshot program using the ACS/HRC that has a demonstrated
discovery potential an order of magnitude higher than the HST
observations that have already discovered the majority of known
transneptunian binaries. With this continuation we seek to reach the
original goals of this project: to accumulate a sufficiently large
sample in each of the distinct populations collected in the Kuiper
Belt to be able to measure, with statistical significance, how the
fraction of binaries varies as a function of their particular
dynamical paths into the Kuiper Belt. Today's Kuiper Belt bears the
imprints of the final stages of giant-planet building and migration;
binaries may offer some of the best preserved evidence of that
long-ago era.

ACS/HRC/WFC 10733

CCD Hot Pixel Annealing

Hot pixel annealing will continue to be performed once every 4 weeks.
The CCD TECs will be turned off and heaters will be activated to bring
the detector temperatures to about +20C. This state will be held for
approximately 6 hours, after which the heaters are turned off, the
TECs turned on, and the CCDs returned to normal operating condition.
To assess the effectiveness of the annealing, a bias and four dark
images will be taken before and after the annealing procedure for both
WFC and HRC. The HRC darks are taken in parallel with the WFC darks.
The charge transfer efficiency {CTE} of the ACS CCD detectors declines
as damage due to on-orbit radiation exposure accumulates. This
degradation has been closely monitored at regular intervals, because
it is likely to determine the useful lifetime of the CCDs. We combine
the annealling activity with the charge transfer efficiency monitoring
and also merge into the routine dark image collection. To this end,
the CTE monitoring exposures have been moved into this proposal . 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 both the Wide
Field Channel {WFC}, and the High Resolution Channel {HRC}.

ACS/WFC 10813

MgII Absorption Line Systems: Galaxy Halos or the Metal-Enriched IGM?

MgII QSO absorption lines detected in the spectra of background QSOs
were used over a decade ago to infer that all redshift z 0.2
galaxies have gaseous halos of radius ~ 60 kpc. The actual size of the
halo was believed to be proportional to the luminosity of the galaxy.
However, these conclusions are now much harder to understand in light
of the results from numerical simulations which show how gas evolves
in the universe. These models predict that gas and galaxies merely
share the same filamentary structures defined by dark matter. If these
models are correct, how are MgII systems and galaxies really related?
We can better understand the distribution of absorbing gas if we FIRST
select galaxies close to QSO sightlines and THEN search for MgII
absorption at the redshift of the intervening galaxies. This is the
antithesis of the original experiments which sought to find absorbing
galaxies based on known MgII systems. The frequency with which we
detect MgII lines from randomly selected galaxies should enable us to
better understand if absorption arises in the halos of individual
galaxies, or if MgII merely arises in the same IGM that galaxies
inhabit. We have used ground-based telescopes to indentify twenty z =
0.31-0.55 galaxies within 14-51 kpc of a g 20 QSO, and to search for
MgII absorption at the galaxies' redshifts. Surprisingly, we find that
only 50% of our QSOs show MgII absorption. In this proposal, we seek
multi-color ACS images of twelve of the fields to i} correlate the
incidence of MgII with galaxy morphology; ii} determine if absorption
{or lack thereof} is related to galaxy disks or halos; iii} search for
signs of galaxy interactions which may explain the large
cross-sections of MgII systems; and iv} look for faint interloping
galaxies closer to the line of sight than the one we identified. An
important component of the program is to observe each field in the
SDSS g-, r- and i-bands, to permit an estimate of the photometric
redshift of any objects which lie closer to the QSO sightline than the
identified galaxy, and which might actually be responsible for the
absorption.

NIC1 10879

A search for planetary-mass companions to the nearest L dwarfs -
completing the survey

We propose to extend the most sensitive survey yet undertaken for very
low-mass companions to ultracool dwarfs. We will use NICMOS to
complete imaging of an all-sky sample of 87 L dwarfs in 80 systems
within 20 parsecs of the Sun. The combination of infrared imaging and
proximity allows us to search for companions with mass ratios q0.25
at separations exceeding ~3 AU, while probing companions with q0.5 at
~1.5 AU separation. This resolution is crucial, since no ultracool
binaries are known in the field with separations exceeding 15 AU.
Fifty L dwarfs from the 20-parsec sample have high-resolution imaging,
primarily through our Cycle 13 HST proposal which identified six new
binaries, including an L/T system. Here, we propose to target the
remaining 30 dwarfs

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark 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 POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword 'USEAFTER=date/time' will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting
in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at
redshifts exceeding 1 are now the leading obstacles to determining the
nature of dark energy. We propose a single, integrated set of
observations for Cycle 15 that will provide a 40% improvement in
constraints on dark energy. This program will observe known Cepheids
in six reliable hosts of Type Ia supernovae with NICMOS, reducing the
uncertainty in H_0 by a factor of two because of the smaller
dispersion along the instability strip, the diminished extinction, and
the weaker metallicity dependence in the infrared. In parallel with
ACS, at the same time the NICMOS observations are underway, we will
discover and follow a sample of Type Ia supernovae at z 1. Together,
these measurements, along with prior constraints from WMAP, will
provide a great improvement in HST's ability to distinguish between a
static, cosmological constant and dynamical dark energy. The Hubble
Space Telescope is the only instrument in the world that can make
these IR measurements of Cepheids beyond the Local Group, and it is
the only telescope in the world that can be used to find and follow
supernovae at z 1. Our program exploits both of these unique
capabilities of HST to learn more about one of the greatest mysteries
in science.

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 07 07
FGS REacq 04 04
OBAD with Maneuver 24 24

SIGNIFICANT EVENTS: (None)

 




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