Mass distribution and structural parameters of Small Magellanic Cloud star clusters

Abstract

In this work, we estimate, for the first time, the total masses and mass function (MF) slopes of a sample of 29 young and intermediate-age Small Magellanic Cloud (SMC) clusters from CCD Washington photometry. We also derive age, interstellar reddening and structural parameters for most of the studied clusters by employing a statistical method to remove the unavoidable field star contamination. Only these 29 clusters out of 68 originally analysed cluster candidates present stellar overdensities and coherent distribution in their colour-magnitude diagrams compatible with the existence of a genuine star cluster.We employed simple stellar population models to derive general equations for estimating the cluster mass based only on its age and integrated light in the B, V, I, C and T1 filter. These equations were tested against mass values computed from luminosity functions, showing an excellent agreement. The sample contains clusters with ages between 60 Myr and 3 Gyr and masses between 300 and 3000M⊙ distributed between ~0°.5 and ~2° from the SMC optical centre. We determined MF slopes for 24 clusters, of which 19 have slopes compatible with that of Kroupa's initial mass function (α = 2.3 ± 0.7), considering the uncertainties. The remaining clusters - H86-188, H86-190, K47, K63 and NGC 242 - showed flatter MFs. Additionally, only clusters with masses lower than ~1000M⊙ and flatter MF were found within ~0.°6 from the SMC rotational centre. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.