HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4567
PERIOD
COVERED: UT March 13, 2008 (DOY 073)
OBSERVATIONS
SCHEDULED
ACS/SBC
11151
Evaluating
the Role of Photoevaporation of Protoplanetary Disk Dispersal
Emission
produced by accretion onto the central star leads to
photoevaporation,
which may play a fundamental role in disk dispersal.
Models
of disk photoevaporation by the central star are challenged by
two
potential problems: the emission produced by accretion will be
substantially
weaker for low-mass stars, and photoevaporation must
continue
as accretion slows. Existing FUV spectra of CTTSs are biased to
solar-mass
stars with high accretion rates, and are therefore
insufficient
to address these problems. We propose use HST/ACS SBC
PR130L
to obtain FUV spectra of WTTSs and of CTTSs at low masses and
mass
accretion rates to provide crucial data to evaluate
photoevaporation
models. We will estimate the FUV and EUV luminosities
of
low-mass CTTSs with small mass accretion rates, CTTSs with transition
disks
and slowed accretion, and of magnetically-active WTTSs.
ACS/SBC
11325
Improved
Sensitivity Calibration of SBC Prisms
We
propose to improve the sensitivity calibration of the SBC PR110L and
PR130L
prisms by observing an additional calibrator target. Observations
with
the ACS/SBC PR110L of two G-type stars (GO-10114, GO-10718) showed
a
pronounced peak of counts at wavelength of about 3500A. An analysis of
the
existing flux standard star observations showed that this peak is
mainly
caused by a red leak (increased sensitivity of the MAMA
detectors).
Additionally, there are indications of a scattered light
component
which is worse for bluer stars. With this proposal we aim to
improve
on the existing sensitivity calibrations for wavelength greater
than
1800A in order to better characterize the red leak. Existing
observations
of flux standard stars are covering rather blue white dwarf
stars.
In this proposal we aim to observe a much redder star. The most
suitable
star we identified is 16 Cyg B, a solar analog.
WFPC2
10905
The
Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region
With
accurate distances, the nearest groups of galaxies can be resolved
in
3 dimensions and the radial component of the motions of galaxies due
to
local density perturbations can be distinguished from cosmological
expansion
components. Currently, with the ACS, galaxy distances within 8
Mpc
can be measured effectively and efficiently by detecting the tip of
the
red giant branch {TRGB}. Of four principal groups at high galactic
latitude
in this domain, the Canes Venatici I Group {a} is the least
studied,
{b} is the most populated, though overwhelmingly by dwarf
galaxies,
and {c} is likely the least dynamically evolved. It is
speculated
that galaxies in low mass groups may fail to retain baryons
as
effectively as those in high mass groups, resulting in significantly
higher
mass-to-light ratios. The CVn I Group is suspected to lie in the
mass
regime where the speculated astrophysical processes that affect
baryon
retention are becoming important.
FGS
11212
Filling
the Period Gap for Massive Binaries
The
current census of binaries among the massive O-type stars is
seriously
incomplete for systems in the period range from years to
millennia
because the radial velocity variations are too small and the
angular
separations too close for easy detection. Here we propose to
discover
binaries in this observational gap through a Faint Guidance
Sensor
SNAP survey of relatively bright targets listed in the Galactic O
Star
Catalog. Our primary goal is to determine the binary frequency
among
those in the cluster/association, field, and runaway groups. The
results
will help us assess the role of binaries in massive star
formation
and in the processes that lead to the ejection of massive
stars
from their natal clusters. The program will also lead to the
identification
of new, close binaries that will be targets of long term
spectroscopic
and high angular resolution observations to determine
their
masses and distances. The results will also be important for the
interpretation
of the spectra of suspected and newly identified binary
and
multiple systems.
NIC1
11057
Cycle
15 NICMOS dark current, shading profile, and read noise monitoring
program
The
purpose of this proposal is to monitor the dark current, read noise,
and
shading profile for all three NICMOS detectors throughout the
duration
of Cycle 15. This proposal is a slightly modified version of
proposal
10380 of cycle 13 and 9993 of cycle12 and is the same as Cycle
14.
that we cut down some exposure time to make the observation fit
within
24 orbits.
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.
NIC2
11157
NICMOS
Imaging Survey of Dusty Debris Around Nearby Stars Across the
Stellar
Mass Spectrum
Association
of planetary systems with dusty debris disks is now quite
secure,
and advances in our understanding of planet formation and
evolution
can be achieved by the identification and characterization of
an
ensemble of debris disks orbiting a range of central stars with
different
masses and ages. Imaging debris disks in starlight scattered
by
dust grains remains technically challenging so that only about a
dozen
systems have thus far been imaged. A further advance in this field
needs
an increased number of imaged debris disks. However, the technical
challenge
of such observations, even with the superb combination of HST
and
NICMOS, requires the best targets. Recent HST imaging investigations
of
debris disks were sample-limited not limited by the technology used.
We
performed a search for debris disks from a IRAS/Hipparcos cross
correlation
which involved an exhaustive background contamination check
to
weed out false excess stars. Out of ~140 identified debris disks, we
selected
22 best targets in terms of dust optical depth and disk angular
size.
Our target sample represents the best currently available target
set
in terms of both disk brightness and resolvability. For example, our
targets
have higher dust optical depth, in general, than newly
identified
Spitzer disks. Also, our targets cover a wider range of
central
star ages and masses than previous debris disk surveys. This
will
help us to investigate planetary system formation and evolution
across
the stellar mass spectrum. The technical feasibility of this
program
in two-gyro mode guiding has been proven with on-orbit
calibration
and science observations during HST cycles 13, 14, and 15.
NIC2
11219
Active
Galactic Nuclei in nearby galaxies: a new view of the origin of
the
radio-loud radio-quiet dichotomy?
Using
archival HST and Chandra observations of 34 nearby early-type
galaxies
{drawn from a complete radio selected sample} we have found
evidence
that the radio-loud/radio-quiet dichotomy is directly connected
to
the structure of the inner regions of their host galaxies in the
following
sense: [1] Radio-loud AGN are associated with galaxies with
shallow
cores in their light profiles [2] Radio-quiet AGN are only
hosted
by galaxies with steep cusps. Since the brightness profile is
determined
by the galaxy's evolution, through its merger history, our
results
suggest that the same process sets the AGN flavour. This
provides
us with a novel tool to explore the co-evolution of galaxies
and
supermassive black holes, and it opens a new path to understand the
origin
of the radio-loud/radio-quiet AGN dichotomy. Currently our
analysis
is statistically incomplete as the brightness profile is not
available
for 82 of the 116 targets. Most galaxies were not observed
with
HST, while in some cases the study is obstructed by the presence of
dust
features. We here propose to perform an infrared NICMOS snapshot
survey
of these 82 galaxies. This will enable us to i} test the reality
of
the dichotomic behaviour in a substantially larger sample; ii} extend
the
comparison between radio-loud and radio-quiet AGN to a larger range
of
luminosities.
WFPC2
11022
WFPC2
Cycle 15 Decontaminations and Associated Observations
This
proposal is for the WFPC2 decons. Also included are instrument
monitors
tied to decons: photometric stability check, focus monitor,
pre-
and post-decon internals {bias, intflats, kspots, & darks}, UV
throughput
check, VISFLAT sweep, and internal UV flat check.
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 time.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11221
- GSACQ(1,3,1) fine lock backup on FGS 1 while LOS
GSAcq(1,3,1) at 07:56:27 acquired in fine lock backup on FGS 1
only,
with QF3STOPF and QSTOP flags set. No other flags were seen.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
12
12
FGS
REacq
02
02
OBAD
with Maneuver
28
28
SIGNIFICANT
EVENTS: (None)