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Daily Report #4510



 
 
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Old December 19th 07, 02:22 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #4510

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4510

PERIOD COVERED: UT December 18, 2007 (DOY 352)

OBSERVATIONS SCHEDULED

ACS/SBC 11199

A Hard Look at Stellar Disks at the Epoch of Planet Formation

We propose to use HST/ACS/SBC and Chandra/ACIS-S3 to observe the high
energy fluxes of 4 stars surrounded by disks in the newly discovered
aggregate 25 Ori, the most populous 10 Myr group known within 500 pc.
Our observations will cover the 1-25A and 1250-2000A bandpasses, and
will complement our optical and Spitzer data for these objects, to
provide essential input to physically-consistent models of disk
structure and chemistry in the age range around 10 Myr, thought to be
a critical period in the planet- forming process. We will be able to
determine the Ne/O ratio and determine if the anomalous metal
abundances observed in X-ray spectra of young stars are an
evolutionary or an environmental effect. Our proposed observations
will double the number of 10 Myr old accreting stars with known high
energy radiation fields, and will be the first FUV observations of low
mass accreting stars in an OB association.

FGS 11211

An Astrometric Calibration of Population II Distance Indicators

In 2002 HST produced a highly precise parallax for RR Lyrae. That
measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful result, judged by the over ten refereed citations each year
since. It is, however, unsatisfactory to have the direct,
parallax-based, distance scale of Population II variables based on a
single star. We propose, therefore, to obtain the parallaxes of four
additional RR Lyrae stars and two Population II Cepheids, or W Vir
stars. The Population II Cepheids lie with the RR Lyrae stars on a
common K-band Period-Luminosity relation. Using these parallaxes to
inform that relationship, we anticipate a zero-point error of 0.04
magnitude. This result should greatly strengthen confidence in the
Population II distance scale and increase our understanding of RR
Lyrae star and Pop II Cepheid astrophysics.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

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 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 anytime.

WFPC2 11128

Time Scales Of Bulge Formation In Nearby Galaxies

Traditionally, bulges are thought to fit well into galaxy formation
models of hierarchical merging. However, it is now becoming well
established that many bulges formed through internal, secular
evolution of the disk rather than through mergers. We call these
objects pseudobulges. Much is still unknown about pseudobulges, the
most pressing questions being: How, exactly, do they build up their
mass? How long does it take? And, how many exist? We are after an
answer to these questions. If pseudobulges form and evolve over longer
periods than the time between mergers, then a significant population
of pseudobulges is hard to explain within current galaxy formation
theories. A pseudobulge indicates that a galaxy has most likely not
undergone a major merger since the formation of the disk. The ages of
pseudobulges give us an estimate for the time scale of this quiescent
evolution. We propose to use 24 orbits of HST time to complete UBVIH
imaging on a sample of 33 nearby galaxies that we have observed with
Spitzer in the mid-IR. These data will be used to measure spatially
resolved stellar population parameters {mean stellar age, metallicity,
and star formation history}; comparing ages to star formation rates
allows us to accurately constrain the time scale of pseudobulge
formation. Our sample of bulges includes both pseudo- and classical
bulges, and evenly samples barred and unbarred galaxies. Most of our
sample is imaged, 13 have complete UBVIH coverage; we merely ask to
complete missing observations so that we may construct a uniform
sample for studying bulge formation. We also wish to compare the
stellar population parameters to a variety of bulge and global galaxy
properties including star formation rates, dynamics, internal bulge
morphology, structure from bulge-disk decompositions, and gas content.
Much of this data set is already or is being assembled. This will
allow us to derive methods of pseudobulge identification that can be
used to accurately count pseudobulges in large surveys. Aside from our
own science goals, we will present this broad set of data to the
community. Thus, we waive proprietary periods for all observations.

WFPC2 11222

Direct Detection and Mapping of Star Forming Regions in Nearby,
Luminous Quasars

We propose to carry out narrow-band emission line imaging observations
of 8 quasars at z=0.05-0.15 with the WFPC2 ramp filters and with the
NICMOS narrow-band filters. We will obtain images in the [O II], [O
III], H-beta, and Pa-alpha emission line bands to carry out a series
of diagnostic tests aimed at detecting and mapping out star-forming
regions in the quasar host galaxies. This direct detection of
star-forming regions will confirm indirect indications for star
formation in quasar host galaxies. It will provide a crucial test for
models of quasar and galaxy evolution, that predict the co-existence
of starbursts and "monsters" and will solve the puzzle of why
different indicators of star formation give contradictory results. A
secondary science goal is to assess suggested correlations between
quasar luminosity and the size of the narrow-line region.

WFPC2 11344

Velocity Gradients in the Jets of BL Lac Objects

We propose to observe the arcsec-scale jets of 2 BL Lac objects with
highly relativistic jets (bulk Lorentz factor of 16) on parsec scales
in order to determine whether a velocity gradient exists between the
axis and edge of the jet and along the length of the jet. Models both
for the morphology of jets in BL Lac objects and for the launching of
the jet predict such gradients. If radio-selected BL Lac objects are
end-on FR 1 sources, there should be strong X-ray emission from
inverse Compton scattering of CMB photons along the highly beamed fast
spine of the jet. The imaging observations with Chandra, HST, SST, and
the VLA will therefore verify whether such a spine exists and on what
length scale it decelerates to nonrelativistic speeds.

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:

17597-9 - FHST Stuck-on-Bottom Macro Execution

COMPLETED OPS NOTES: (None)

*********************** SCHEDULED***** SUCCESSFUL

FGS GSacq*************** 05*************** 05
FGS REacq*************** 11*************** 11
OBAD with Maneuver* **** 32*************** 32

SIGNIFICANT EVENTS: (None)


 




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