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

TL;DR

This study uses HST ACS data to catalog 339 star clusters in M31, revealing their color, age, and mass distributions, and providing insights into their formation and destruction processes.

Contribution

It presents a comprehensive ACS-based survey of M31 star clusters, expanding on previous WFPC2 results and offering new data on cluster properties and evolution.

Findings

Identification of 339 star clusters in M31.

Discovery of a peak in intermediate-age, intermediate-mass clusters.

Observation of a wide color range indicating diverse ages and reddening.

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.