Identification and Analysis of Young Star Cluster Candidates in M31

Abstract

We present a method for finding clusters of young stars in M31 using broadband WFPC2 data from the HST data archive. Applying our identification method to 13 WFPC2 fields, covering an area of ~60 arcmin², has revealed 79 new candidate young star clusters in these portions of the M31 disk. Most of these clusters are small (<~5 pc), young (~10-200 Myr) star groups located within large OB associations. We have estimated the reddening values and the ages of each candidate individually by fitting isochrones to the stellar photometry. We provide a catalog of the candidates including rough approximations of their reddenings and ages. We also look for patterns of cluster formation with galactocentric distance, but our rough estimates are not precise enough to reveal any clear patterns. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.