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Daily Report # 4347



 
 
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Old April 24th 07, 06:28 PM posted to sci.astro.hubble
Cooper, Joe
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Posts: 568
Default Daily Report # 4347

Notice: For the foreseeable future, the daily reports may contain apparent
discrepancies between some proposal descriptions and the listed instrument
usage. This is due to the conversion of previously approved ACS WFC or HRC
observations into WFPC2, or NICMOS observations subsequent to the loss of
ACS CCD science capability in late January.


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4347

PERIOD COVERED: UT April 23, 2007 (DOY 113)

OBSERVATIONS SCHEDULED

WFPC2 10798

Dark Halos and Substructure from Arcs & Einstein Rings

The surface brightness distribution of extended gravitationally lensed arcs
and Einstein rings contains super-resolved information about the lensed
object, and, more excitingly, about the smooth and clumpy mass distribution
of the lens galaxies. The source and lens information can non-parametrically
be separated, resulting in a direct "gravitational image" of the inner
mass-distribution of cosmologically-distant galaxies {Koopmans 2005;
Koopmans et al. 2006 [astro-ph/0601628]}. With this goal in mind, we propose
deep HST ACS-F555W/F814W and NICMOS-F160W WFC imaging of 20 new
gravitational-lens systems with spatially resolved lensed sources, of the 35
new lens systems discovered by the Sloan Lens ACS Survey {Bolton et al.
2005} so far, 15 of which are being imaged in Cycle-14. Each system has been
selected from the SDSS and confirmed in two time- efficient HST-ACS snapshot
programs {cycle 13&14}. High-fidelity multi-color HST images are required
{not delivered by the 420s snapshots} to isolate these lensed images
{properly cleaned, dithered and extinction-corrected} from the lens galaxy
surface brightness distribution, and apply our "gravitational maging"
technique. Our sample of 35 early-type lens galaxies to date is by far the
largest, still growing, and most uniformly selected. This minimizes
selection biases and small-number statistics, compared to smaller, often
serendipitously discovered, samples. Moreover, using the WFC provides
information on the field around the lens, higher S/N and a better understood
PSF, compared with the HRC, and one retains high spatial resolution through
drizzling. The sample of galaxy mass distributions - determined through this
method from the arcs and Einstein ring HST images - will be studied to: {i}
measure the smooth mass distribution of the lens galaxies {dark and luminous
mass are separated using the HST images and the stellar M/L values derived
from a joint stellar-dynamical analysis of each system}; {ii} quantify
statistically and individually the incidence of mass-substructure {with or
without obvious luminous counter- parts such as dwarf galaxies}. Since
dark-matter substructure could be more prevalent at higher redshift, both
results provide a direct test of this prediction of the CDM hierarchical
structure-formation model.

ACS/SBC 10815

The Blue Hook Populations of Massive Globular Clusters

Blue hook stars are a class of hot {~35,000 K} subluminous horizontal branch
stars that have been recently discovered using HST ultraviolet images of the
globular clusters omega Cen and NGC 2808. These stars occupy a region of the
HR diagram that is unexplained by canonical stellar evolution theory. Using
new theoretical evolutionary and atmospheric models, we have shown that the
blue hook stars are very likely the progeny of stars that undergo extensive
internal mixing during a late helium core flash on the white dwarf cooling
curve. This "flash mixing" produces an enormous enhancement of the surface
helium and carbon abundances, which suppresses the flux in the far
ultraviolet. Although flash mixing is more likely to occur in stars that are
born with high helium abundances, a high helium abundance, by itself, does
not explain the presence of a blue hook population - flash mixing of the
envelope is required. We propose ACS ultraviolet {SBC/F150LP} observations
of the five additional globular clusters for which the presence of blue hook
stars is suspected from longer wavelength observations. Like omega Cen and
NGC 2808, these five targets are also among the most massive globular
clusters, because less massive clusters show no evidence for blue hook
stars. Because our targets span 1.5 dex in metallicity, we will be able to
test our prediction that flash-mixing should be less drastic in metal-rich
blue hook stars. In addition, our observations will test the hypothesis that
blue hook stars only form in globular clusters massive enough to retain the
helium-enriched ejecta from the first stellar generation. If this hypothesis
is correct, then our observations will yield important constraints on the
chemical evolution and early formation history in globular clusters, as well
as the role of helium self-enrichment in producing blue horizontal branch
morphologies and multiple main sequence turnoffs. Finally, our observations
will provide new insight into the formation of the hottest horizontal branch
stars, with implications for the origin of the hot helium-rich subdwarfs in
the Galactic field.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 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 {both gain 7 and gain
15 -- to test stability of gains and bias levels}, a test for quantum
efficiency in the CCDs, and a monitor for possible buildup of contaminants
on the CCD windows. These also provide raw data for generating annual
super-bias reference files for the calibration pipeline.

FGS 11019

Monitoring FGS1r's Interferometric Response as a Function of Spectral Color

This proosal uses FGS1r in Transfer mode to observe standard single stars of
a variety of spectral types to obtain point source interferograms for the
Transfer mode calibration library. In specific cases, the calibration star
will also be observed in POS mode multiple times with the F583W and F5ND
elements to provide the data to verify the stabiligy of the cross filter
calibration.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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.

WFPC2 10884

The Dynamical Structure of Ellipticals in the Coma and Abell 262 Clusters

We propose to obtain images of 13 relatively luminous early type galaxies in
the Coma cluster and Abell 262 for which we have already collected ground
based major and minor axis spectra and images. The higher resolution HST
images will enable us to study the central regions of these galaxies which
is crucial to our dynamical modelling. The complete data set will allow us
to perform a full dynamical analysis and to derive the dark matter content
and distribution, the stellar orbital structure, and the stellar population
properties of these objects, probing the predictions of galaxy formation
models. The dynamical analysis will be performed using an up-to-date
axi-symmetric orbit superposition code.

WFPC2 11023

WFPC2 CYCLE 15 Standard Darks - part 1

This dark calibration program obtains dark frames every week in order to
provide 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 data will also provide a monitor of radiation damage to the
CCDs.

WFPC2 11032

CTE Extended Targets Closeout

Measuring the charge transfer efficiency {CTE} of an astronomical CCD camera
is crucial to determining the CCD's photometric fidelity across the field of
view. WFPC2's CTE has degraded steadily over the last 13 years because of
continuous exposure to trapped particles in HST's radiation environment. The
fraction of photometric signal lost from WFPC2's CTI {change transfer
inefficiency} is a function of WFPC2's time in orbit, the integrated signal
in the image, the location of the image on the CCD, and the background
signal. Routine monitoring of WFPC2's degrading CTE over the last 13 years
has primarily concerned the effects of CTI on point-source photometry.
However, most of the sources imaged by WFPC2 are extended rather than
point-like. This program aims to characterize the effects of CTI on the
photometry and morphology of extended sources near the end of WFPC2's
functional life. Images of a standard field within the rich galaxy cluster
Abell 1689 are recorded with each WFPC2 camera using the F606W and F814W
filters. These images will be compared with contemporaneous images of Abell
1689 recorded with the field rotated by approximately 180 degrees to assess
differences between extended sources imaged near and far from the serial
register. The images will also be compared with similar images recorded in
Cycle 8 {Program 8456} to characterize the rate of CTE degradation over the
lifetime of WFPC2.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS},
a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100
early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e.,
0.1"-1"}, the HST brightness profiles vary systematically from the
brightest giants {which have nearly constant surface brightness cores} to
the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the
fraction of galaxy mass contributed by the nuclei in the faint galaxies is
identical to that contributed by supermassive black holes in the bright
galaxies {0.2%}. These findings strongly suggest that a single mechanism is
responsible for both types of Central Massive Object: most likely internally
or externally modulated gas inflows that feed central black holes or lead to
the formation of "nuclear star clusters". Understanding the history of gas
accretion, star formation and chemical enrichment on subarcsecond scales has
thus emerged as the single most pressing question in the study of nearby
galactic nuclei, either active or quiescent. We propose an ambitious HST
program {199 orbits} that constitutes the next, obvious step forward:
high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging
for the complete ACSVCS sample. By capitalizing on HST's unique ability to
provide high-resolution images with a sharp and stable PSF at UV and IR
wavelengths, we will leverage the existing optical HST data to obtain the
most complete picture currently possible for the history of star formation
and chemical enrichment on these small scales. Equally important, this
program will lead to a significant improvement in the measured structural
parameters and density distributions for the stellar nuclei and the
underlying galaxies, and provide a sensitive measure of "frosting" by young
stars in the galaxy cores. By virtue of its superb image quality and stable
PSF, NICMOS is the sole instrument capable of the IR observations proposed
here. In the case of the WFPC2 observations, high-resolution UV imaging {
0.1"} is a capability unique to HST, yet one that could be lost at any any
time.

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 11 11
FGS REacq 04 04
OBAD with Maneuver 25 25

SIGNIFICANT EVENTS:

Evaluation of Universal Kalman Filter performance continued. Multiple text
segments were executed, all of them successfully. Details follow.

The Kalman Filter was restarted at 113/13:17 (OR 18046-0) during orbit day
and during an M2G guiding interval. The filter was activated with the MSS,
CSS and Gyro-1 sensor inputs enabled. All UKF parameters showed nominal
convergence and steady-state operation. The test was an MSS/CSS/Gyro-1
Initialization Test Case with the spacecraft inertially fixed during a fast
changing B-field in orbit day (MC_G1_INF, Test #17). The KF was halted at
14:10 and reconfigured back to the default MSS/CSS configuration.

The Gyro-1 sensor input was added to the KF at 113/15:00 (OR 18047-0) during
orbit day and during a T2G guiding interval. The filter was running with the
MSS and CSS sensor inputs enabled and converged. All UKF parameters showed
nominal operation. The test was an MSS/CSS Test Case with the Gyro-1 sensor
input added to an already converged filter. The spacecraft was inertially
fixed during a fast changing B-field in orbit day (MC_G1_RNF, Test #29). The
Gyro-1 input was removed at 16:10 during an F2G period in orbit day to
reconfigure the KF back to default MSS/CSS configuration.

The Kalman Filter was restarted at 113/18:44 (OR 18045-0) just prior to
orbit night entry (approx. 1 minute) and during an F2G guiding interval and
with the spacecraft inertially fixed (M_C_INP, Test #10). The filter was
activated with the default configuration of MSS and CSS sensor inputs
enabled. The test was executed to monitor the initial nominal convergence of
the filter as it crossed the EON penumbra. The filter began to converge
initially, paused and two minutes after EON it continued toward convergence.
All UKF parameters showed nominal steady-state operation.

The Kalman Filter was restarted at 113/20:01 (OR 18046-0) during orbit day
and during an M2G guiding interval. The filter was activated with the MSS,
CSS and Gyro-1 sensor inputs enabled. All UKF parameters showed nominal
convergence and steady-state operation. The test was an MSS/CSS/Gyro-1
Initialization Test Case with the spacecraft inertially fixed during a slow
changing B-field in orbit day (M_G1_INS, Test #18). The KF was halted at
20:35 and reconfigured back to the default MSS/CSS configuration.

The Gyro-1 sensor input was added to the KF at 113/21:46 (OR 18047-0) during
orbit day and during a M2G guiding interval. The filter was running with the
MSS and CSS sensor inputs enabled and converged. All UKF parameters showed
nominal operation. The test was an MSS/CSS Test Case with the Gyro-1 sensor
input added to an already converged filter. The spacecraft was inertially
fixed during a slow changing B-field in orbit day (M_G1_RNS, Test #30). The
KF was halted at 23:20 and reconfigured back to the default MSS/CSS
configuration.

The Kalman Filter was restarted at 113/23:34 (OR 18045-0) during orbit night
and during an T2G guiding interval. The filter was activated with the MSS
and CSS sensor inputs enabled. The KF was restarted as the OBAD-1 correction
maneuver was occurring and all the UKF parameters showed nominal convergence
and steady-state operation. The test was an MSS/CSS Initialization Test Case
with the spacecraft inertially fixed during a slow changing B-field in orbit
night (M_0_INS, Test #4). The test may be re-executed as the intent was to
execute with the spacecraft inertially fixed.

The Gyro-1 sensor input was added to the KF at 113/23:55 (OR 18048-2) during
orbit night and during an F2G guiding interval. The filter was running with
the MSS and CSS sensor inputs enabled and converged. The Gyro-1 sensor input
was later removed at 114/01:18 to monitor the response of the filter when
the gyro input is removed during orbit night with a slow changing B-field
and no vehicle maneuver occurring (M_G1_HNS, Test #26). All UKF parameters
showed nominal operation.

The test above completed testing for the day and left the KF configured in
the default MSS/CSS mode
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