Young Star Clusters: Metallicities, Ages and Masses

Abstract

Observations of Young Star Cluster (YSC) systems in inter-acting galaxies are reviewed with particular emphasis on their Luminosity Functions (LF) and colour distributions. A few spectroscopic abundance measurements are available. They will be compared to YSC abundance predictions from spiral galaxy models. Evolutionary synthesis models allow to derive ages for individual YSCs on the basis of their broad band colours. With individual YSC ages models predict the future colour and luminosity evolution of the YSC systems that will be compared - after a Hubble time - to observations of old Globular Cluster (GC) systems. Using model M/L ratios as a function of age, YSC masses can be estimated. Age spread effects in young systems can cause the shape of the LF to substantially differ from the shape of the underlying mass function. Major sources of uncertainty are the metallicity, dust reddening, and observational colour uncertainties.