THE LUMINOSITY, MASS, AND AGE DISTRIBUTIONS OF COMPACT STAR CLUSTERS IN M83 BASED ON HUBBLE SPACE TELESCOPE/WIDE FIELD CAMERA 3 OBSERVATIONS

The newly installed Wide Field Camera 3 (WFC3) on the Hubble Space Telescope has been used to obtain multi-band images of the nearby spiral galaxy M83. These new observations are the deepest and highest resolution images ever taken of a grand-design spiral, particularly in the near-ultraviolet, and allow us to better differentiate compact star clusters from individual stars and to measure the luminosities of even faint clusters in the U band. We find that the luminosity function (LF) for clusters outside of the very crowded starburst nucleus can be approximated by a power law, dN/dL proportional to L(alpha), with alpha = -2.04 +/- 0.08, down to M(V) approximate to -5.5. We test the sensitivity of the LF to different selection techniques, filters, binning, and aperture correction determinations, and find that none of these contribute significantly to uncertainties in alpha. We estimate ages and masses for the clusters by comparing their measured UBVI, H alpha colors with predictions from single stellar population models. The age distribution of the clusters can be approximated by a power law, dN/d tau proportional to tau(gamma), with gamma = -0.9 +/- 0.2, for M greater than or similar to few x 10(3) M(circle dot) and tau less than or similar to 4 x 10(8) yr. This indicates that clusters are disrupted quickly, with approximate to 80%-90% disrupted each decade in age over this time. The mass function of clusters over the same M-tau range is a power law, dN/dM proportional to M(beta), with beta = -1.94 +/- 0.16, and does not have bends or show curvature at either high or low masses. Therefore, we do not find evidence for a physical upper mass limit, MC, or for the earlier disruption of lower mass clusters when compared with higher mass clusters, i.e., mass-dependent disruption. We briefly discuss these implications for the formation and disruption of the clusters.