A variation of the fraction of stars that form in bound clusters within M83

Abstract

Recent observations, as well as theoretical studies, have suggested that stellar cluster formation may depend on local and global environmental properties. In particular, the fraction of stars that form within long-lived bound clusters (\Gamma) may depend on environment, with indications that it may be higher in the more extreme environments of high star-formation rate density galaxies. How \Gamma varies has important implications on the use of clusters to determine the star-formation histories of galaxies as well as our understanding of the star-formation process itself. Previous studies have estimated \Gamma over full galaxies, making it difficult to discern the physical cause of the reported variations. Here, we use existing star cluster catalogues and HST-WFC3 V and I images of the grand design, face-on spiral galaxy M83 in order to see if and how \Gamma varies within a single galaxy. We find that \Gamma decreases strongly as a function of galactocentric radius, by a factor of ~5 over the inner ~6kpc, in agreement with recent theoretical predictions and decreasing trends observed in the gas surface density of the galaxy.