Daily Report #4567

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 images. 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)