The Star Clusters of the Small Magellanic Cloud: Structural Parameters

Abstract

We present structural parameters for 204 stellar clusters in the Small Magellanic Cloud derived from fitting King and Elson, Fall, & Freeman model profiles to the V-band surface brightness profiles as measured from the Magellanic Clouds Photometric Survey images. Both King and EFF profiles are satisfactory fits to the majority of the profiles although King profiles are generally slightly superior to the softened power-law profiles of Elson, Fall, and Freeman and provide statistically acceptable fits to ~90% of the sample. We find no correlation between the preferred model and cluster age. The only systematic deviation in the surface brightness profiles that we identify is a lack of a central concentration in a subsample of clusters, which we designate as "ring" clusters. In agreement with previous studies, we find that the clusters in the SMC are significantly more elliptical than those in the Milky Way. However, given the mean age difference and the rapid destruction of these systems, the comparison between SMC and MW should not directly be interpreted as either a difference in the initial cluster properties or their subsequent evolution. We find that cluster ellipticity correlates with cluster mass more strongly than with cluster age. We identify several other correlations (central surface brightness vs. local background density, core radius vs. tidal force, size vs. distance) that can be used to constrain models of cluster evolution in the SMC.