Daily #4027

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4027

PERIOD COVERED: UT January 012, 2006 (DOY 012)

OBSERVATIONS SCHEDULED

ACS/SBC 10259

Planetary nebulae in the SMC: a study of stellar evolution and
populations in an extremely low- metallicity environment

The final phase of the evolution of low- and intermediate-mass stars,
the planetary nebula {PN} ejection, is thought to largely contribute
to the carbon and nitrogen enrichment in galaxies, in particular in
old stellar populations. Stellar generations forming from a carbon-
and nitrogen- enriched medium are a necessary condition for planetary
and life formation. It is essential to understand how stars go through
the process of shedding their chemically-enriched shells, and to test
the predictions of stellar evolution theory on the relationship
between stellar mass and elemental enrichment. Magellanic Cloud PNs
are ideal probes for this study. Their abundances can be directly
related to the mass of the central stars and to that of the stellar
progenitor, without the great {distance and reddening} uncertainties
that affect Galactic PNs. The UV lines are essential for calculating
the abundances of the element related to stellar evolution {C, N, O}
and to progenitor populations {e.g., Ne}. We propose to acquire STIS
UV spectroscopy of the SMC PNs whose morphology and central star
properties has been previously determined by us with HST. We will
derive the {C, N, O} abundance-to-mass relation, and determine the
extent to which the mass of the progenitors of asymmetric PNs exceed
that of symmetric PNs. We will also test the PN luminosity function,
and probe cosmic recycling, in a very low-metallicity environment.

ACS/WFC 10524

Blue Stragglers: a key stellar population to probe internal cluster
dynamics

This proposal is part of a coordinated project devoted to understand
the interplay of globular cluster {GC} dynamics and the formation and
evolution of blue straggler stars {BSS}. By using a combination of HST
and ground-based observations we are constructing complete BSS surveys
in a sample of GCs; complete BSS surveys require mid-UV HST
observations in the center and wide field CCD ground based
observations under excellent seeing conditions of the exterior. Up to
now only four clusters have been surveyed in this way and the results
are surprising: in three GCs {M3, 47 Tuc, NGC 6752} we have discovered
that the BSS radial distribution is bimodal, highly peaked in the
cluster center, rapidly decreasing at intermediate radii and rising
again at large radii {Ferraro et al. 1997, 2004, Sabbi et al. 2004},
conversely BSS population in Omega Centauri does not show any
signature of the segregation which would be expected for a class of
objects arising from either stellar interactions or binarity {Ferraro
et al. 2005}. These observational facts are opening a new prospective
in the study of the formation processes and evolution of BSS in GCs.
By using extensive simulations, we demonstrated that the spatial
distribution of BSS observed in 47 Tuc can be only reproduced if a
sizable fraction of BSS is generated {via mass transfer in primordial
binaries} in the peripheral region of the cluster {Mapelli et al
2004}, thus excluding a purely collisional formation scenario. Here we
propose mid-UV imaging of a few clusters suspected of harboring a
large population of central BSS and a few known to have many BSS the
external region. These are good candidates for determining accurate
BSS radial distributions. The modest amount of time proposed here will
go far to determine the ubiquity of BSS bimodality and to constrain
models of dynamical evolution. Since we believe the proposed
observations would be useful to the entire stellar community {for
multifold purposes} we waive the propretary period.

ACS/WFC 10543

Microlensing in M87 and the Virgo Cluster

Resolving the nature of dark matter is an urgent problem. The results
of the MACHO survey of the Milky Way dark halo toward the LMC indicate
that a significant fraction of the halo consists of stellar mass
objects. The VATT/Columbia survey of M31 finds a similar lens fraction
in the M31 dark halo. We propose a series of observations with ACS
that will provide the most thorough search for microlensing toward
M87, the central elliptical galaxy of the Virgo cluster. This program
is optimized for lenses in the mass range from 0.01 to 1.0 solar
masses. By comparing with archival data, we can detect lenses as
massive as 100 solar masses, such as the remnants of the first stars.
These observations will have at least 15 times more sensitivity to
microlensing than any previous survey, e.g. using WFPC2. This is due
to the factor of 2 larger area, factor of more than 4 more sensitivity
in the I-band, superior pixel scale and longer baseline of
observations. Based on the halo microlensing results in the Milky Way
and M31, we might expect that galaxy collisions and stripping would
populate the overall cluster halo with a large number of stellar mass
objects. This program would determine definitively if such objects
compose the cluster dark matter at the level seen in the Milky Way. A
negative result would indicate that such objects do not populate the
intracluster medium, and may indicate that galaxy harassment is not as
vigorous as expected. We can measure the level of events due to the
M87 halo: this would be the best exploration to date of such a lens
population in an elliptical galaxy. Star-star lensing should also be
detectable. About 20 erupting classical novae will be seen, allowing
to determine the definitive nova rate for this giant elliptical
galaxy. We will determine if our recent HST detection of an M87
globular cluster nova was a fluke, or indicative of a 100x higher rate
of incidence of cataclysmic variables and nova eruptions in globulars
than previously believed. We will examine the populations of variable
stars, and will be able to cleanly separate them from microlensing.

ACS/WFC 10595

A Reference Database for Accurate Ages and Metallicities of Globular
Clusters in the Magellanic Clouds

We propose to finalize the compilation of a comprehensive database of
high-quality ages and metallicities of Simple Stellar Populations
{SSPs} in the Milky Way and the Magellanic Clouds. We will acquire new
ACS imagery for 8 young and intermediate-age globular clusters in the
Magellanic Clouds to create high-quality color-magnitude diagrams
{CMDs} to enable accurate measurements of their ages and
metallicities. In concert with a similar analysis of CMD data already
available in the HST archive for 8 more such GCs, the resulting
database will provide a well-sampled coverage of the full range of
ages and metallicities known among globular clusters {0.5 = Age {Gyr}
= 13.5 and -2.3 = [Fe/H] = +0.1, respectively}. This database will
form the crucial basis for our ongoing, comprehensive multi-wavelength
program to: {1} establish empirical relations among SSP colors {from
the UV [GALEX] through the mid-IR [Spitzer]}, line strengths, ages and
metallicities, and {2} provide a stringent test of the systemic
accuracy of age and metallicity determinations using state-of-the-art
population synthesis models.

ACS/WFC/WFPC2 10499

Life Before the Fall: Morphological Evolution of Galaxies in Groups
Prior to Cluster Assembly at z=0.37

We propose to obtain a deep ACS/WFC mosaic of a protocluster comprised
of 4 distinct galaxy groups that are gravitationally bound to each
other at z=0.37. The galaxy groups have a total combined mass
comparable to the Coma cluster and already have twice as many
absorption line galaxies as the field. The SG1120 complex thus
provides an unprecedented opportunity for determining whether
"pre-processing" in the group environment is responsible for the bulk
of observed diffences between galaxies in nearby clusters and those in
the field. High resolution imaging with HST is needed to
morphologically classify the group members and measure their
structural parameters. By combining the early-type fraction and
morphology-density relation in SG1120 with results from our wide-field
spectroscopic survey, we will test whether spectral and morphological
transformation timescales are decoupled on group scales and isolate
the environmental mechanisms responsible for such evolution. We will
also measure the Fundamental Plane and M/L ratios of the early-type
members to constrain their formation epoch and how their stellar
populations have evolved. Observations of the multiple galaxy groups
in SG1120 provide a unique dataset to the community and will aid our
understanding of how galaxies evolve in the still poorly studied group
regime.

FGS 10613

Calibrating the Mass-Luminosity Relation at the End of the Main
Sequence

We propose to use HST-FGS1R to calibrate the mass-luminosity relation
{MLR} for stars less massive than 0.2 Msun, with special emphasis on
objects near the stellar/brown dwarf border. Our goals are to
determine M_V values to 0.05 magnitude, masses to 5 than double the
number of objects with masses determined to be less than 0.20 Msun.
This program uses the combination of HST-FGS3/FGS1R at optical
wavelengths and ground-based infrared interferometry to examine
nearby, subarcsecond binary systems. The high precision measurements
with HST-FGS3/FGS1R {to 1 mas in the separations} for these faint
targets {V = 10--15} simply cannot be equaled by any ground based
technique. As a result of these measurements, we are deriving high
quality luminosities and masses for the components in the observed
systems, and characterizing their spectral energy distributions from
0.5 to 2.2 Mum. Several of the objects included have M 0.1 Msun,
placing them at the very end of the stellar main sequence. Three of
the targets are brown dwarf candidates, including the current low mass
record holder, GJ 1245C, with a mass of 0.062 +/- 0.004 Msun. The
payoff of this proposal is high because all 10 of the systems selected
have already been resolved with HST- FGS3/FGS1R during Cycles 5--10
and contain most of the reddest objects for which masses can be
determined.

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 10173

Infrared Snapshots of 3CR Radio Galaxies

Radio galaxies are an important class of extragalactic objects: they
are one of the most energetic astrophysical phenomena and they provide
an exceptional probe of the evolving Universe, lying typically in high
density regions but well-represented across a wide redshift range. In
earlier Cycles we carried out extensive HST observations of the 3CR
sources in order to acquire a complete and quantitative inventory of
the structure, contents and evolution of these important objects.
Amongst the results, we discovered new optical jets, dust lanes,
face-on disks with optical jets, and revealed point-like nuclei whose
properties support FR-I/BL Lac unified schemes. Here, we propose to
obtain NICMOS infrared images of 3CR sources with z0.3 as a major
enhancement to an already superb dataset. We aim to deshroud dusty
galaxies, study the underlying host galaxy free from the distorting
effects of dust, locate hidden regions of star formation and establish
the physical characteristics of the dust itself. We will measure
frequency and spectral energy distributions of point-like nuclei,
expected to be stronger and more prevalent in the IR, seek spectral
turnovers in known synchrotron jets and find new jets. We will
strongly test unified AGN schemes and merge these data with existing
X-ray to radio observations. The resulting database will be an
incredibly valuable resource to the astronomical community for years
to come.

NIC3/ACS/WFC 10529

A Deep H-band Probe of the Globular Cluster Mass function

We propose to obtain deep NICMOS H-band data for the globular clusters
in the inner region of M87 and coordinated parallel ACS WFC g and z
band observations of a second field which has very deep archival
NICMOS data. Therefore, our proposed deep NICMOS observation overlaps
corresponding deep archival optical data in the inner regions, and the
parallel ACS observations overlap deep NICMOS images in the outer
field. The combination of the sensitivity of the near infrared to the
mass of old stellar systems such as the globular clusters in M87 and
the ability of the optical to isolate the metal-rich and metal-poor
subcomponents of the globular cluster system will allow us to probe
the mass function, and the possible variation with metallicity, to
unprecedented depths. These observations are critical to linking the
commonly observed cluster luminosity function to the usually derived
mass function in theoretical calculations of globular cluster and
globular cluster system formation and evolution models. The multiple
pointings will allow us to probe the radial variations in globular
cluster properties and test the predictions of cluster formation and
dynamical destruction models. Because of its extremely rich globular
cluster system {~15, 000 clusters} M87 is one of the only galaxies in
which such a study can be conducted with a statistically significant
number of candidate clusters {approximately 300 globular clusters in
this study} with efficient use of HST time.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10078 - REACQ(1,2,2) failed due to search radius limit exceeded on FGS
1 @ 012/10:04:27z REACQ(1,2,2) at 012/09:59:46 failed due to Search
Radius Limit Exceeded on FGS 1 at 10:04:27. Primary GSACQ(1,2,2) at
08:35:09 was successful. OBAD after REACQ at 10:06:59 showed attitude
error of 279.04 arc seconds on V2.

COMPLETED OPS REQUEST:
17619-1 - Software Taper Charge Control @ 012/1156z
17625-0 - Modify SOC Benchmark & ACR 2 HI Limit @ 013/0010z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 07 07
FGS
REacq 09 08 012/10:04:27z
(HSTAR # 10078)
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS:

Taper Charge Transition Flash Report - (12 Jan 2006 08:54:20, SE
dlewis) - On DOY 2006/012 at approximately 13:27 Software Taper Charge
Control was activated via Ops Request 17619. During the first orbit
cycle after the transition, the system performed as expected - ACR set
and reset the benchmark, recharge ratios, and the trickle charge
elapse timer; SPA trim relays opened and closed via OCA. Moreover, the
battery temperatures are slightly cooler, and the system SOC delta
remained within 4 AH of the pre-test value. EPS SEs will continue to
monitor the system and subsequent flash reports are forthcoming.

Flash Report: FSW SOC Changes post-Taper Charge Transition Ops
Briefing - (12 Jan 2006 18:30:53) - Summary Extract Follows --
Discussion/Agreements: The recommendation to reduce the benchmark to
234 Ah so that the end-of-orbit night FSW SOC is ~5 Ah above the
end-of-orbit night pressure-based SOC was approved along with changing
the ACR high limit to 3 batteries reaching cut-off.