The low-mass stellar-mass functions of rich, compact clusters in the Large Magellanic Cloud^*

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: [liuq;licai;huyi]@bao.ac.cn
² Graduate University of the Chinese Academy of Sciences, Beijing 100049, PR China
³ Department of Physics & Astronomy, The University of Sheffield, Sheffield S3 7RH, UK e-mail: R.deGrijs@sheffield.ac.uk
⁴ Département de Physique, de Génie Physique et d'Optique and Centre de Recherche en Astrophysique du Québec, Université Laval, Québec, QC G1V 0A6, Canada

Received: 14 April 2009
Accepted: 22 May 2009

Abstract

Context. The LMC is an ideal environment for studying stellar MFs, because it contains a large population of compact clusters at different evolutionary stages. We aim to obtain constraints on the initial MFs (IMFs) of our sample clusters on the basis of their present-day MFs, combined with our understanding of their dynamical and photometric evolution.

Aims. We use Hubble Space Telescope photometry for six rich, compact star clusters in the Large Magellanic Cloud (LMC), with ages ranging from 0.01 to 1.0 Gyr, to derive the clusters' stellar mass functions (MFs) at their half-mass radii.

Methods. We derived the clusters' present-day MFs below 1.0  using deep observations with the Space Telescope Imaging Spectrograph and updated stellar population synthesis models.

Results. Since the relaxation timescales of low-mass stars are very long, dynamical evolution will not have affected the MFs below 1.0  significantly, so that – within the uncertainties – the derived MFs are consistent with the solar-neighbourhood IMF, at least for the younger clusters. The IMF in the low-density, low-metallicity environment of the LMC disk is not significantly different from the IMF in the solar neighbourhood.