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Session 82 - Spirals & Irregulars.
Display session, Friday, January 09
Exhibit Hall,
We present Faint Object Camera ultraviolet images of Messier 31 and Messier 32. The hot stellar population detected in the composite UV spectra of these nearby galaxies is partially resolved into individual stars, and their individual colors and luminosities are measured. Although our photometry does not extend to the horizontal branch (HB) itself, we can detect and characterize stars that are in the bright phases of post-HB evolution for the entire range of mass on the HB. Many of our detected stars imply the existence of an extended HB in the cores of these galaxies. These hot stars are the extragalactic counterparts to the hot subdwarfs in our own Galactic field, and their confirmed existence in neighboring galaxies supplies an important validation to explanations of the ultraviolet upturn phenomenon found in ellipticals and spiral bulges.
