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
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
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 i
mages.
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
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)