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3984 Daily Report



 
 
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Old November 10th 05, 04:25 PM
Joe Cooper
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Default 3984 Daily Report

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3984

PERIOD COVERED: UT November 8, 2005 (DOY 312)

OBSERVATIONS SCHEDULED

ACS/HRC 10512

Search for Binaries Among Faint Jupiter Trojan Asteroids

We propose an ambitious SNAPSHOT program to survey faint Jupiter Trojan
asteroids for binary companions. We target 150 objects, with the
expectation of acquiring data on about 50%. These objects span Vmag =
17.5-19.5, a range inaccessible with ground-based adaptive optics. We
now have a significant sample from our survey of brighter Trojans to
suggest that the binary fraction is similar to that which we find among
brighter main-belt asteroids, roughly 2%. However, our observations
suggest a higher binary fraction for smaller main-belt asteroids,
probably the result of a different formation mechanism {evident also
from the physical characteristics of the binaries}. Because the
collision environment among the Trojans is similar to that of the Main
Belt, while the composition is likely to be very different, sampling the
binary fraction among the fainter Trojans should help us understand the
collisional and binary formation mechanisms at work in various
populations, including the Kuiper Belt, and help us evaluate theories
for the origin of the Trojans. Calibration of and constraints on models
of binary production and collisional evolution can only be done using
these large-scale, real-life physical systems that we are beginning now
to find and utilize.

ACS/WFC 10523

The Halo Shape and Metallicity of Massive Spiral Galaxies

We propose to resolve the stellar populations of the halos of seven
nearby, massive disk galaxies using a SNAP survey with WFC/ACS. These
observations will provide star counts and color-magnitude diagrams 2-3
magnitudes below the tip of the Red Giant Branch along the two principal
axes and one intermediate axis of each galaxy. We will measure the
metallicity distribution functions and stellar density profiles from
star counts down to very low average surface brightnesses, equivalent to
~31 V-mag per square arcsec. This proposal will create a unique sampling
of galaxy halo properties, as our targets cover a range in galaxy mass,
luminosity, inclination, and morphology. As function of these galaxy
properties this survey will provide:- the first systematic measurement
of radial light profiles and axial ratios of the diffuse stellar halos
and outer disks of spiral galaxies- a comprehensive analysis of halo
metallicity distributions as function of galaxy type and position within
the galaxy- an unprecedented study of the stellar metallicity and age
distribution in the outer disk regions where the disk truncations occur-
the first comparative study of globular clusters and their field stellar
populations We will use these fossil records of the galaxy assembly
process to test halo formation models within the hierarchical galaxy
formation scheme.

ACS/WFC 10526

Dynamics of the Polarization Structure of the Crab Nebula

The Crab Nebula is not a free expansion SNR. Rather, it is a pulsar wind
nebula expanding from the inside out into a larger remnant of freely
expanding ejecta. At the heart of this object is the Crab Pulsar and the
region where the pulsar's highly nonisotropic wind interacts with the
larger synchtron nebula. HST and Chandra monitoring has shown this to be
one of the most intricately structured and highly dynamical objects ever
observed. In Cycle 12 we demonstrated our ability to use the
polarization capabilities of the ACS to isolate physically discrete
features within the Crab Synchrotron Nebula and accurately measure their
polarization characteristics. These data provide a unique look at the
physical structure in the heart of the Crab, adding a new dimension to
past observations. Polarization provides extensive information about
field geometries, the degree of disorder in the field, and particle
pitch angle distributions. But one image of the Crab is like a single
image of waves at the beach. It necessarily misses the point. In the
Crab, the name of the game is "dynamics". In this proposal we request
time to monitor changes in the polarization structure of the Crab. This
program will allow us to follow the changing polarization of features
including relativistically moving wisps in the Crab Nebula. This is the
only place in the sky where a dynamic relativistic plasma can be
observed in sufficient detail to make such measurements possible, and
the HST/ACS is the only instrument that we are likely to see in our
careers capable of making the measurement. These observations will be an
important addition to the already rich observational legacy of HST for
what is arguably the most important single object in astrophysics.

ACS/WFC 10586

The Rosetta Stone without a Distance: Hunting for Cepheids in the
Primordial Galaxy I Zw 18

The Blue Compact Dwarf galaxy I Zw 18 is one of the most intriguing
objects in the Local Universe. It has the lowest nebular metallicity of
all known galaxies {Z=1/32 solar}. It has long been regarded as a
possible example of a galaxy undergoing its first burst of star
formation. However, its real evolutionary state continues to be
controversial. The WFPC2 and NICMOS detection of AGB stars by our group
and others suggested the presence of an underlying older population.
However, deeper ACS observations by Izotov & Thuan {2004} recently
failed to detect the signature of RGB stars. This was interpreted as
confirmation that I Zw 18 is in fact a galaxy "in formation", a local
analog of primordial galaxies in the distant Universe. This result was
widely reported in the international news media. However, an alternative
possibility is that I Zw 18 is somewhat further away than previously
believed, so that Red Giant Branch stars were too faint to detect.
Quoted distances in the literature have ranged from 10 to 20 Mpc. We
intend to resolve this controversy by direct determination of the
distance to 1 Mpc accuracy using Cepheids. For this we request 12 visits
of two orbits each, to execute at carefully planned intervals. We will
obtain V and I band ACS/WFC photometry in each visit. The new data will
be combined with archival data, but we show that the archival data by
themselves are insufficient to achieve our science goals. The distance
will allow us to place I Zw 18 into its proper place in the evolutionary
sequence of galaxy formation.

ACS/WFC 10618

The Light Echoes around V838 Monocerotis: MHD in 3 Dimensions,
Circumstellar Mapping, and Dust

V838 Monocerotis, which burst upon the astronomical scene in early 2002,
is a completely unanticipated new object. It underwent a large-amplitude
and very luminous outburst, during which its spectrum remained that of
an extremely cool supergiant. A rapidly evolving set of light echoes
around V838 Mon was discovered soon after the outburst, and quickly
became the most spectacular display of the phenomenon ever seen. The
light echoes, which were imaged by us with HST during 2002, provide the
means to accomplish four unique types of measurements based on continued
HST imaging during the event: {1} Study effects of MHD turbulence at
high resolution and in 3 dimensions; {2} Construct the first unambiguous
and fully 3-D map of a circumstellar dust envelope in the Milky Way; {3}
Study dust physics in a unique setting where the spectrum and light
curve of the illumination, and the scattering angle, are unambiguously
known; and {4} Determine the distance to V838 Mon through two
independent direct geometric techniques {polarimetry and angular
expansion rates}. Because of the extreme rarity of light echoes, this is
almost certainly the only opportunity to achieve such results during the
lifetime of HST. We propose a campaign during Cycle 14 of imaging the
echoes every 8 days for a total of 6 epochs, in order to fully map a
thin slab through the dust shell and achieve the other goals listed
above.

FGS 10610

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric
elements {perturbation orbit semi-major axis and inclination} of
extra-solar planets orbiting six stars. These companions were originally
detected by radial velocity techniques. We have demonstrated that FGS
astrometry of even a short segment of reflex motion, when combined with
extensive radial velocity information, can yield useful inclination
information {McArthur et al. 2004}, allowing us to determine companion
masses. Extrasolar planet masses assist in two ongoing research
frontiers. First, they provide useful boundary conditions for models of
planetary formation and evolution of planetary systems. Second, knowing
that a star in fact has a plantary mass companion, increases the value
of that system to future extrasolar planet observation missions such as
SIM PlanetQuest, TPF, and GAIA.

NIC2 10527

Imaging Scattered Light from Debris Disks Discovered by the Spitzer
Space Telescope Around 20 Sun-like

We propose to use the high contrast capability of the NICMOS coronagraph
to image a sample of newly discovered circumstellar disks associated
with sun-like stars. These systems were identified by their strong
thermal infrared emission with the Spitzer Space Telescope as part of
the Spitzer Legacy Science program titled, "The Formation and Evolution
of Planetary Systems {FEPS}." Modelling of the thermal excess emission
in the form of spectral energy distributions alone cannot distinguish
between narrowly confined high opacity disks and broadly distributed,
low opacity disks. However, our proposed NICMOS observations can, by
imaging the light scattered from this material. Even non- detections
will place severe constraints on the disk geometry, ruling out models
with high optical depth. Unlike previous disk imaging programs, our
program contains a well defined sample of solar mass stars covering a
range of ages from ~10Myrs to a few Gyrs, allowing us to study the
evolution of disks from primordial to debris for the first time. These
results will greatly improve our understanding of debris disks around
Sun- like stars at stellar ages nearly 10x older than any previous
investigation. Thus we will have fit a crucial piece into the puzzle
concerning the formation and evolution of our own solar system.

NICMOS 8790

NICMOS Post-SAA calibration - CR Persistence Part 1.

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.

WFPC2 10745

WFPC2 CYCLE 14 INTERNAL MONITOR

This calibration proposal is the Cycle 14 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.

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 07 07
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS: (None)

 




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