Daily #4082

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4082

PERIOD COVERED: UT March 30, 2006 (DOY 089)

OBSERVATIONS SCHEDULED

ACS/HRC 10617

HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet

As the nearest galaxy with an optical jet, M87 affords an unparalleled
opportunity to study extragalactic jet phenomena at the highest
resolution. During 2002, HST and Chandra monitoring of the M87 jet
detected a dramatic flare in knot HST-1 located ~1" from the nucleus.
As of late 2004 its brightness has increased fifty-fold in the optical
band, and continues to increase sharply; the X-rays show a similarly
dramatic outburst. In both bands HST-1 now greatly exceeds the nucleus
in brightness. To our knowledge this is the first incidence of an
optical or X-ray outburst from a jet region which is spatially
distinct from the core source -- this presents an unprecedented
opportunity to study the processes responsible for non-thermal
variability and the X-ray emission. We propose seven epochs of
HST/STIS monitoring during Cycle 14, as well as seven epochs of
Chandra/ACIS observation {5ksec each}. We also include a brief HRC/ACS
observations that will be used to gather spectral information and map
the magnetic field structure. The results of this investigation are of
key importance not only for understanding the nature of the X-ray
emission of the M87 jet, but also for understanding flares in blazar
jets, which are highly variable, but where we have never before been
able to resolve the flaring region in the optical or X-rays. These
observations will allow us to test synchrotron emission models for the
X-ray outburst, constrain particle acceleration and loss timescales,
and study the jet dynamics associated with this flaring component.

ACS/HRC/WFC 10514

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the
early dynamical evolution of the outer Solar System. We propose a
Snapshot program using the ACS/HRC that has a potential discovery
efficiency an order of magnitude higher than the HST observations that
have already discovered the majority of known transneptunian binaries.
By more than doubling the number of observed objects in dynamically
hot and cold subpopulations we will be able to answer, with
statistical significance, the question of whether these groups differ
in the abundance of binaries as a result of their particular dynamical
paths into the Kuiper Belt. Today's Kuiper Belt bears the imprints of
the final stages of giant-planet building and migration; binaries may
offer some of the best preserved evidence of that long-ago era.

ACS/WFC 10591

ACS Observations of the Galaxies in A Giant Ly-alpha Nebula at z~2.7

Giant Ly-alpha nebulae appear to be sites of ongoing massive galaxy
formation, as evidenced by their association with very luminous,
young, star-forming galaxies and large galaxy overdensities. However
the origin of the extended gas and the source of ionization remain
mysterious. We have discovered a ~200 kpc size nebula which appears to
contain a number of embedded sources, including a very obscured,
luminous mid-infrared source and a Lyman break galaxy. We propose to
obtain deep ACS and NICMOS images of this nebula in order to: {i}
determine the spatial morphology of the Ly-alpha emission on sub-kpc
scales; {ii} precisely locate the known continuum sources within the
nebula; {ii} determine their morphologies; {iii} detect the source of
ionizing photons at the very center of the nebula; {iv} constrain the
ionizing luminosity contributed by a possible distributed population
of faint, compact continuum sources in the nebula; and {v} by SED
fitting of population synthesis models, constrain the ages of the
ionizing sources with the aim of determining the timescale of the
galaxy formation process in the nebula.

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/HRC 10536

What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey

Essentially all planetary nebulae {PNs} are aspherical, whereas the
mass-loss envelopes of AGB stars are strikingly spherical. Our
previous SNAPshot surveys of a morphologically unbiased sample of
pre-planetary nebulae {PPNs} -- objects in transition between the AGB
and PN evolutionary phases -- show that roughly half our observed
targets are resolved, with bipolar or multipolar morphologies.
Spectroscopic observations of our sample confirm that these objects
have not yet evolved into planetary nebulae. Thus, the transformation
from spherical to aspherical geometries has already fully developed by
the time these dying stars have become PPNs. Although our current
studies have yielded exciting results, they are limited in two
important ways -- {1} the number of well-resolved objects is still
small {18}, and the variety of morphologies observed relatively
multitudinous, hence no clear trends can yet be established between
morphology and other source properties {e.g., near-IR, far-IR colors,
stellar spectral type, envelope mass}, and {2} the current samples are
strongly biased towards small PPNs, as inferred from their low
60-to-25 micron flux ratios [R{60/25}1]. However, the prototype of
objects with R{60/25}1, the Frosty Leo Nebula, has a puzzlingly large
post-AGB age {almost 10^4 yr} and a fairly cool central star, very
different from the expectations of single-star stellar evolutionary
models. A proposed, but still speculative, hypothesis for such objects
is that the slow evolution of the central star is due to backflow of
material onto the mass-losing star, retarding its evolution towards
the PN phase. This hypothesis has significant consequences for both
stellar and nebular evolution. We therefore propose a survey of PPNs
with R{60/25}1 which is heavily weighted towards the discovery of
such "stalled PPNs". Supporting kinematic observations using long-slit
optical spectroscopy {with the Keck}, millimeter and radio
interferometric observations {with OVRO, VLA & VLBA} are being
undertaken. The results from this survey {together with our previous
work} will allow us to draw general conclusions about the complex
mass-outflow processes affecting late stellar evolution, and will
provide crucial input for theories of post-AGB stellar evolution. Our
survey will produce an archival legacy of long-standing value for
future studies of dying stars.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

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 10519

Testing the Stellar Coalescence and Accretion Disk Theories of Massive
Star Formation with NICMOS

The importance of massive stars cannot be underestimated - they
produce most of the heavy elements in the universe and dominate the
evolution of the interstellar medium in their vicinity. In spite of
their significance, our understanding of their formation is meager.
Both accretion through disks, analogous to the process of low-mass
star formation, and coalescence of low-mass stars through collisions
in the dense cores of stellar clusters have been suggested. Possibly
both mechanisms occur. High spatial resolution polarization
measurements of the closest massive young stellar objects {YSOs} will
enable us to search for evidence of disk accretion or coalescence in
the form of patterns indicative of light scattered off a coherent disk
or off a disk disrupted by an infalling star, respectively. Here we
propose to use 2 micron polarimetry with NICMOS to identify the
presence of accretion disks around massive YSOs or to characterize
their environments as possibly disrupted from a close stellar
encounter. There are only a few sources that meet the stringent
selection criteria for this investigation {even with HST}, which we
will examine here. High spatial resolution is required, but even more
important, the point spread function {PSF} must be stable with time.
Furthermore, the PSF must put minimal flux into large spatial scales,
something that cannot be achieved with adaptive optics. This
combination of high Strehl ratio and stable PSF can only be achieved
from space.

WFPC2 10751

WFPC2 CYCLE 14 Intflat Linearity Check and Filter Rotation Anomaly
Monitor

Intflat observations will be taken to provide a linearity check: the
linearity test consists of a series of intflats in F555W, in each gain
and each shutter. A combination of intflats, visflats, and earthflats
will be used to check the repeatability of filter wheel motions.
{Intflat sequences tied to decons, visits 1-18 in prop 10363, have
been moved to the cycle 14 decon proposal 10744 for easier
scheduling.} Note: long-exposure WFPC2 intflats must be scheduled
during ACS anneals to prevent stray light from the WFPC2 lamps from
contaminating long ACS external exposures.

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:
17681-0 - Genslew for proposal 10487 - slot 6 @ 089/19:54z
17682-0 - Genslew for proposal 10487 - slot 5 @ 089/19:57z
17684-0 - Genslew for proposal 10487 - slot 4 @ 089/19:59z
17685-0 - Genslew for proposal 10487 - slot 3 @ 089/20:00z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 09 09
FGS REacq 06 06
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS: (None)