Daily Report #4433

Notice: Due to the conversion of some ACS WFC or HRC observations into
WFPC2, or NICMOS observations after the loss of ACS CCD science
capability in January, there may be an occasional discrepancy between
a proposal's listed (and correct) instrument usage and the abstract
that follows it.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4433

PERIOD COVERED: UT August 23, 2007 (DOY 235)

OBSERVATIONS SCHEDULED

WFPC2 10787

Modes of Star Formation and Nuclear Activity in an Early Universe
Laboratory

Nearby compact galaxy groups are uniquely suited to exploring the
mechanisms of star formation amid repeated and ongoing gravitational
encounters, conditions similar to those of the high redshift universe.
These dense groups host a variety of modes of star formation, and they
enable fresh insights into the role of gas in galaxy evolution. With
Spitzer mid-IR observations in hand, we have begun to obtain high
quality, multi-wavelength data for a well- defined sample of 12 nearby
{4500km/s} compact groups covering the full range of evolutionary
stages. Here we propose to obtain sensitive BVI images with the
ACS/WFC, deep enough to reach the turnover of the globular cluster
luminosity function, and WFPC2 U-band and ACS H-alpha images of
Spitzer-identified regions hosting the most recent star formation. In
total, we expect to detect over 1000 young star clusters forming
inside and outside galaxies, more than 4000 old globular clusters in
40 giant galaxies {including 16 early-type galaxies}, over 20 tidal
features, approximately 15 AGNs, and intragroup gas in most of the 12
groups. Combining the proposed ACS images with Chandra observations,
UV GALEX observations, ground-based H-alpha imaging, and HI data, we
will conduct a detailed study of stellar nurseries, dust, gas
kinematics, and AGN.

WFPC2 10901

UV-Luminous Globular Clusters in NGC 1399

Ultraviolet observations have revealed remarkable diversity among old
stellar populations in globular clusters and E/S0 galaxies. We
recently discovered with HST/STIS that globular clusters in the giant
elliptical galaxy M87 have the most heavily populated hot horizontal
branches of any stellar systems yet studied. Their far-UV/optical
colors are up to 1 mag bluer than any Milky Way globular cluster and
approach the theoretical limits for production of hot-HB stars in old
stellar populations. The differences among the metal-poor clusters are
particularly interesting, because it is thought that these objects
reflect the earliest stages of galaxy formation at high redshifts.
Here we propose deep ACS far-UV imaging of a second gE galaxy, NGC
1399, with a cluster system that is well-studied at longer
wavelengths, to determine whether it shares characteristics with M87.
These observations bear on aspects of advanced stellar evolution, on
the histories of globular clusters in different environments, and on
the interpretation of the "ultraviolet upturn'' phenomenon in
elliptical galaxies and its value as a population probe in distant
galaxies.

WFPC2 11039

Polarizers Closeout

Observations of standard stars and a highly polarized reflection
nenula are made as a final calibration for the WFPC2 polarizers.
VISFLATS are also obtained.

WFPC2 11291

Following Eta Carinae's Change of State

Eta Carinae is now known to be undergoing some unusually rapid changes
on a timescale of several years. They are probably essential for
modeling the star's long-term recovery from its Giant Eruption 160
years ago -- the prototype "supernova impostor" event. Since high
spatial resolution is needed to isolate the central star, and the
present state will probably not recur in the future, it is important
to obtain HST data during the next two years. We propose a
cost-effective set of ACS observations with three goals: {1} to obtain
a continuing record of the star's rapid UV and visual brightening; {2}
to lengthen the temporal baseline of ACS images enough to settle an
important question concerning ejecta ages; and {3} to extend the
record of morphological changes in the inner ejecta past the midpoint
of eta Car's 5.5-year cycle.

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: (None)

COMPLETED OPS NOTES: (None)

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

SIGNIFICANT EVENTS: (None)