Mass, Age, and Space Distributions of Star Clusters

Abstract

This article reviews some recent studies of the mass, age, and space distributions of star clusters, with a primary focus on the large population of clusters in the interacting Antennae galaxies. Some of the highlights of these studies are the following: 1. The mass function of the young clusters (with ages τ< 10^8 yr) has power-law form, dN/dM propto M^{-2}, over the observed range of masses, 10^4 < M < 10^6 solar masses. 2. The age distribution of the clusters declines steeply at all ages, roughly as dN/d tau propto tau^{-1} for mass-limited samples, indicating rapid disruption of most clusters. 3. At least 20% and possibly all stars form in clusters and/or associations, including those that are unbound and short-lived. 4. Many of the clusters that remain bound just after their formation are disrupted on longer timescales by a combination of mass loss by stellar evolution and several stellar dynamical processes. 5. The young clusters have a clumpy space distribution and are located preferentially in regions of high interstellar density, at least when averaged over scales of about a kpc. 6. The positions of the young clusters, however, are not correlated with the local velocity gradients or velocity dispersions in the interstellar medium. There are growing indications that most of these conclusions also apply to the populations of young star clusters in other galaxies, both interacting and quiescent.