THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. III. MEASURING AGES AND MASSES OF PARTIALLY RESOLVED STELLAR CLUSTERS

Abstract

The apparent age and mass of a stellar cluster can be strongly affected by\nstochastic sampling of the stellar initial mass function, when inferred from\nthe integrated color of low mass clusters (less than ~10^4 solar masses). We\nuse simulated star clusters to show that these effects are minimized when the\nbrightest, rapidly evolving stars in a cluster can be resolved, and the light\nof the fainter, more numerous unresolved stars can be analyzed separately. When\ncomparing the light from the less luminous cluster members to models of\nunresolved light, more accurate age estimates can be obtained than when\nanalyzing the integrated light from the entire cluster under the assumption\nthat the initial mass function is fully populated. We show the success of this\ntechnique first using simulated clusters, and then with a stellar cluster in\nM31. This method represents one way of accounting for the discrete, stochastic\nsampling of the stellar initial mass function in less massive clusters and can\nbe leveraged in studies of clusters throughout the Local Group and other nearby\ngalaxies.\n