Daily #4096

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4096

PERIOD COVERED: UT April 19, 2006 (DOY 109)

OBSERVATIONS SCHEDULED

ACS/HRC 10602

A Complete Multiplicity Survey of Galactic O2/O3/O3.5 Stars with ACS

Massive stars are preferentially formed in compact multiple systems
and clusters and many of them remain spatially unresolved to date,
even in our Galaxy. This has hindered the determination of the stellar
upper mass limit. The lack of an accurate knowledge of the
multiplicity of massive stars can also introduce biases in the
calculation of the IMF at its high-mass end. We have recently used
ACS/HRC to resolve HD 93129 A, the earliest O-type star known in the
Galaxy, into a 55 mas binary. We propose here to extend that work into
a complete multi-filter ACS imaging survey of all {20} known
O2/O3/O3.5 Galactic stars to characterize the multiplicity of the most
massive stars. The data will be combined with existing FGS
observations to explore as large a parameter range as possible and to
check for consistency. We will also derive the IMF of each system
using a crowded-field photometry package and processing the data with
CHORIZOS, a code that can derive stellar temperatures, extinctions,
and extinction laws from multicolor photometry.

ACS/HRC 10627

A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae

We propose an ACS/HRC snapshot survey of 50 post-AGB sources, objects
which have evolved from the AGB but may or may not become planetary
nebulae {PNe}. This survey will complement existing HST images of
proto-planetary nebulae {PPNe} and PNe in addressing circumstellar
envelope morphology as a function of: 1} the progenitor star mass; 2}
the chemical composition; and 3} evolutionary stage. We will connect
the observed diversity of nebualar shapes with the main physical and
chemical conditions characterizing post-AGB objects, to identify the
mechanism that breaks the symmetry of AGB mass loss. To our knowledge,
no previous HST projects have been specifically designed to address
this issue. From our database of 360 post-AGB candidates, we have
selected approximately 50 targets, none of which have been or are
being observed with HST, to sample different central star masses,
chemical compositions, and evolutionary stages, uniformly across the
sky. These new data will also provide important constraints to a
quantitative analysis of Spitzer Space Telescope {SST} observations
planned for a similar sample of objects. We will model the HST images
and SST spectra using our axisymmetric dust code 2-Dust, to derive
dust density distributions, pole to equator density ratios, dust shell
masses, inclination angles as well as dust composition.

ACS/HRC 10752

Cycle 14 Focus Monitor

The focus of HST is measured primarily with ACS/HRC over full CVZ
orbits to obtain accurate mean focus values via a well sampled
breathing curve. Coma and astigmatism are also determined from the
same data in order to further understand orbital effects on image
quality and optical alignments. To monitor the stability of ACS to
WFPC2 relative focii, we've carried over from previous focus monitor
programs parallel observations taken with the two cameras at suitable
orientations of previously observed targets, and interspersed them
with the HRC CVZ visits.

ACS/HRC/WFC 10758

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The
first half of the program has a different proposal number: 10729.

ACS/WFC 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with
Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful
"dust free" Type Ia supernovae {SNe Ia} dataset than available with
the previous GOODS searches. Moreover, this approach provides a
strikingly more efficient search-and-follow-up that is primarily pre-
scheduled. The resulting dark energy measurements do not share the
major systematic uncertainty at these redshifts, that of the
extinction correction with a prior. By targeting massive galaxy
clusters at z 1 we obtain a five-times higher efficiency in
detection of Type Ia supernovae in ellipticals, providing a
well-understood host galaxy environment. These same deep cluster
images then also yield fundamental calibrations required for future
weak lensing and Sunyaev-Zel'dovich measurements of dark energy, as
well as an entire program of cluster studies. The data will make
possible a factor of two improvement on supernova constraints on dark
energy time variation, and much larger improvement in systematic
uncertainty. They will provide both a cluster dataset and a SN Ia
dataset that will be a longstanding scientific resource.

ACS/WFC 10592

An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in
the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared
selected galaxies exceeds that of optically selected galaxies. These
`luminous infrared galaxies' {LIRGs} are primarily interacting or
merging disk galaxies undergoing enhanced star formation and Active
Galactic Nuclei {AGN} activity, possibly triggered as the objects
transform into massive S0 and elliptical merger remnants. We propose
ACS/WFC imaging of a complete sample of 88 L_IR 10^11.4 L_sun
luminous infrared galaxies in the IRAS Revised Bright Galaxy Sample
{RBGS: i.e., 60 micron flux density 5.24 Jy}. This sample is ideal
not only in its completeness and sample size, but also in the
proximity and brightness of the galaxies. The superb sensitivity,
resolution, and field of view of ACS/WFC on HST enables a unique
opportunity to study the detailed structure of galaxies that sample
all stages of the merger process. Imaging will be done with the F439W
and F814W filters {B and I-band} to examine as a function of both
luminosity and merger state {i} the evidence at optical wavelengths of
star formation and AGN activity and the manner in which instabilities
{bars and bridges} in the galaxies may funnel material to these active
regions, {ii} the relationship between star formation and AGN
activity, and {iii} the structural properties {AGN, bulge, and disk
components} and fundamental parameters {effective radius and surface
brightness} of LIRGs and their similarity with putative evolutionary
byproducts {elliptical, S0 and classical AGN host galaxies}. This HST
survey will also bridge the wavelength gap between a Spitzer imaging
survey {covering seven bands in the 3.6-160 micron range} and a GALEX
UV imaging survey of these galaxies, but will resolve complexes of
star clusters and multiple nuclei at resolutions well beyond the
capabilities of either Spitzer or GALEX. The combined datasets will
result in the most comprehensive multiwavelength study of interacting
and merging galaxies to date.

ACS/WFC 10775

An ACS Survey of Galactic Globular Clusters

We propose to conduct an ACS/WFC imaging survey of Galactic globular
clusters. We will construct the most extensive and deepest set of
photometry and astrometry to-date for these systems reaching a main
sequence mass of ~0.2 solar mass with S/N = 10. We will combine these
data with archival WFPC2 and STIS images to determine proper motions
for the stars in our fields. The resultant cleaned cluster CMDs will
allow us to study a variety of scientific questions. These include
[but are not limited to] 1} the determination of cluster ages and
distances 2} the construction of main sequence mass functions and the
issue of mass segregation 3} the internal motions and dynamical
evolution of globular clusters, and 4} absolute cluster motions,
orbits, and the Milky Way gravitational potential. We anticipate that
the unique resource provided by the proposed treasury archive will
play a central role in the field of globular cluster studies for
decades, with a stature comparable to that of the Hubble Deep Field
for high redshift studies.

ACS/WFC 10992

Investigating the Disintegration of Comet 73P/Schwassmann-Wachmann 3

The performance of the comet 73P/Schwassmann-Wachmann 3 during its
current apparition is vastly surpassing all of our original
expectations. Thus, the currently approved Hubble program to observe
this comet {GO-10625} is no longer adequate, and we propose a 5-orbit
DD program to perform an intensive investigation of the 3 brightest
fragments, all of which are showing evidence for ongoing disruption.
The Hubble observations of 73P/SW3 will produce the most detailed
views possible of the regions surrounding these 3 fragments, thereby
yielding important new insights into cometary disruption, which is one
of the principal mechanisms by which cometary nuclei expire. The
combination of Hubble and Spitzer data, the latter from a recently
approved Spitzer DD program, should provide the most extensive
investigation yet of a cometary disruption event.

NIC1 10143

Ultracool companions to the nearest L dwarfs

We propose to conduct the most sensitive survey to date for low mass
companions to nearby L dwarfs. We will use NICMOS to image targets
drawn from a volume-complete sample of 70 L dwarfs within 20 parsecs.
The combination of infrared imaging and proximity will allow us to
search for T dwarf companions at separations as small as 1.6 AU. This
is crucial, since no ultracool binaries are currently known with
separations exceeding 15 AU. Only 10 dwarfs in this sample have
previous HST observations primarily at optical wavelengths. With the
increased sensitivity of our survey, we will provide the most
stringent test to date of brown dwarf models which envisage formation
as ejected stellar embryos. In addition, our observations will be
capable of detecting binaries with mass ratios as low as 0.3, and will
therefore also test the apparent preference for equal-mass ultracool
binaries. Finally, our observations offer the best prospect to date of
detecting companions significantly cooler than the coolest t dwarf
currently known.

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.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

10229 - GSACQ(2,1,1) fine lock backup on FGS 2,scan step limit
exceeded on FGS 1 @109/2158z

Upon acquisition of signal at 109/21:58:15 HST was in fine lock on FGS
2 only. GSACQ(2,1,1) at 109/21:31:57 ended in fine lock backup on FGS
2 due to scan step limit exceeded on FGS 1.

COMPLETED OPS REQUEST:
17724-2 - HST-WSC RF Test @109/1657z
17727-0 - Table Dump 320@ 109/2040z
17726-0 - Genslew for Proposal 10114-Slot 6 @ 109/2207z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 08
FGS REacq 06 06
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)