The star cluster formation history of the LMC

TL;DR

This study compiles a new catalogue of LMC star clusters to analyze their formation history, dissolution rates, and mass functions, revealing insights into cluster longevity, formation bursts, and the impact of gas expulsion.

Contribution

It provides the first comprehensive analysis of LMC star cluster ages, masses, and dissolution rates, highlighting the rapid loss of clusters and a significant formation burst around 1 Gyr ago.

Findings

Approximately 15% of stars formed in long-lived clusters.

Cluster mass function follows a power-law with slope -2.3 for <1 Gyr.

Over 90% of clusters are lost per dex of age after 200 Myr.

Abstract

The Large Magellanic Cloud is one of the nearest galaxies to us and is one of only few galaxies where the star formation history can be determined from studying resolved stellar populations. We have compiled a new catalogue of ages, luminosities and masses of LMC star clusters and used it to determine the age distribution and dissolution rate of LMC star clusters. We find that the frequency of massive clusters with masses M>5000 Msun is almost constant between 10 and 200 Myr, showing that the influence of residual gas expulsion is limited to the first 10 Myr of cluster evolution or clusters less massive than 5000 Msun. Comparing the cluster frequency in that interval with the absolute star formation rate, we find that about 15% of all stars in the LMC were formed in long-lived star clusters that survive for more than 10 Myr. We also find that the mass function of LMC clusters younger than 1 Gyr can be fitted by a power-law mass function with slope \alpha=-2.3, while older clusters follow a significantly shallower slope and interpret this is a sign of the ongoing dissolution of low-mass clusters. Our data shows that for ages older than 200 Myr, about 90% of all clusters are lost per dex of lifetime. The implied cluster dissolution rate is significantly faster than that based on analytic estimates and N-body simulations. Our cluster age data finally shows evidence for a burst in cluster formation about 1 Gyr ago, but little evidence for bursts at other ages.