An analysis of the population of extended main sequence turn-off clusters in the Large Magellanic Cloud

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 thegenesis of eMSTOs. Indeed, clusters in our sample have core radii, masses and age-relaxationtime 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 resultsincluding 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.