Star cluster evolution in the Magellanic Clouds revisited

TL;DR

This study re-evaluates star cluster evolution in the Magellanic Clouds using homogeneous data, finding limited infant mortality and providing new estimates of cluster disruption timescales.

Contribution

It offers a self-consistent analysis of cluster age and mass distributions, challenging previous high infant mortality rates and estimating initial cluster mass functions.

Findings

SMC cluster infant mortality is at most ~30% between 3-160 Myr.

High cluster mortality rate (>90%) per decade is statistically ruled out.

LMC cluster population shows less than 10% infant mortality.

Abstract

The evolution of star clusters in the Magellanic Clouds has been the subject of significant recent controversy, particularly regarding the importance and length of the earliest, largely mass-independent disruption phase (referred to as "infant mortality"). Here, we take a fresh approach to the problem, using a large, independent, and homogeneous data set of UBVR imaging observations, from which we obtain the cluster age and mass distributions in both the Large and Small Magelanic Clouds (LMC, SMC) in a self-consistent manner. We conclude that the (optically selected) SMC star cluster population has undergone at most ~30% (1sigma) infant mortality between the age range from about 3-10 Myr, to that of approximately 40-160 Myr. We rule out a 90% cluster mortality rate per decade of age (for the full age range up to 10^9 yr) at a >6sigma level. Using a simple approach, we derive a "characteristic" cluster disruption time-scale for the cluster population in the LMC that implies that we are observing the INITIAL cluster mass function. Preliminary results suggest that the LMC cluster population may be affected by <10% infant mortality.