NASA Hubble Space Telescope 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 DAILY REPORT # 4433
– Continuing to collect World Class Science
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)
