An HST Survey of the Disk Cluster Population of M31. II. ACS Pointings

Abstract

This paper reports on a survey of star clusters in M31 based on archival images from the Hubble Space Telescope. Paper I (Krienke and Hodge 2007) reported results from images obtained with the Wide Field/Planetary Camera 2 (WFPC2) and this paper reports results from the Advanced Camera for Surveys (ACS). The ACS survey has yielded a total of 339 star clusters. The color- integrated magnitude diagram of clusters shows three significant features: (1) a group of very red, luminous objects: the globular clusters, (2) a wide range in color for the fainter clusters, representing a considerable range in age and reddening, and (3) a maximum density of intermediate-age, intermediate-mass clusters with ages close to 500 million years and masses of about 2000 solar masses. We give a brief qualitative interpretation of the distribution of clusters in the CMDs in terms of their formation and destruction rates.