Stellar Populations in the Phoenix Dwarf (DIRR/DSPH) Galaxy as Observed by Hubble Space Telescope WFPC2

We present Hubble Space Telescope Wide Field Planetary Camera 2 photometry of the central regions of the Phoenix dwarf galaxy. Accurate photometry allows us to (1) confirm the existence of the horizontal branch previously detected by ground-based observations and use it to determine a distance to Phoenix, (2) clearly detect the existence of multiple ages in the stellar population of Phoenix, (3) determine a mean metallicity of the old red giant branch stars in Phoenix and suggest that Phoenix has evolved chemically over its lifetime, and (4) extract a rough star formation history for the central regions, which suggests that Phoenix has been forming stars roughly continuously over its entire lifetime. Based on observations with the NASA /ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.