An Analysis of the Population of Extended Main Sequence Turn-off Clusters in the Large Magellanic Cloud

TL;DR

This study analyzes the extended main sequence turn-off (eMSTO) phenomenon in Large Magellanic Cloud clusters, finding it is likely due to stellar evolution effects rather than age spreads or cluster properties.

Contribution

It provides the largest sample analysis showing eMSTO is unrelated to cluster core radii, masses, or dynamical state, supporting a stellar evolutionary origin.

Findings

eMSTO is not caused by age spreads within clusters.

Cluster core radii, masses, and dynamical states are unrelated to eMSTO.

FWHM at the MSTO correlates strongly with cluster age.

Abstract

We combine a number of recent studies of the extended main sequence turn-off (eMSTO) phenomenon in intermediate age stellar ($1-2$ Gyr) clusters in the Large Magellanic Cloud (LMC) in order to investigate its origin. By employing the largest sample of eMSTO LMC clusters so far used, we show that cluster core radii, masses, and dynamical state are not related to the genesis of eMSTOs. Indeed, clusters in our sample have core radii, masses and age-relaxation time ratios in the range $\approx$ 2--6 pc, 3.35- 5.50 (log($M_{cls}$/$M_\odot$) and 0.2-8.0, respectively. These results imply that the eMSTO phenomenon is not caused by actual age spreads within the clusters. Furthermore, we confirm from a larger cluster sample recent results including young eMSTO LMC clusters, that the FWHM at the MSTOs correlates most strongly with cluster age, suggesting that a stellar evolutionary effect is the underlying cause.