Star Clusters in Interacting Galaxies: The Case of M51

Abstract

We present the results of an analysis of a population of stellarclusters in the interacting galaxy, M51, using HST-WFPC2 observations.The observations were made in five broad band filters; f336w (U), f439w(B), f555w (V), f675w (R), f814w (I), and transformed to the closestcorresponding Cousins-Johnson filter magnitude using the equationsdefined by Holtzmann [5]. Only sources that were found in every filterwere analysed. By comparing the spectral energy distribution (SED) ofeach source with those of evolutionary spectral synthesis models [4], wehave derived an age, mass, and extinction for each source. Thecomparison was done using the 3DEF method [2], that is based on a least{χ}^2 test. Only sources that were well-fit ( {χ}^2\_{$u$} {\le}1.0)and resolved (fwhm {\ge}1.5 pixels [1]) were used in this study. 533sources pass these criteria, and will be referred to as clusters for theremainder of the paper. With this sample we are able to study thecluster formation history, the cluster initial mass function (cIMF), andsearch for evidence of cluster disruption.