Theoretical Models of Young Open Star Clusters: Effects of a Gaseous Component and Gas Removal

We construct a family of semi-analytic models for young open clusters, including a gaseous component and varying assumptions about the distribution function for the stellar component. The parameters of these models are informed by observed open clusters and general theoretical considerations regarding cluster formation. We use this framework to estimate the fraction of the stellar component that remains gravitationally bound after the gaseous component disperses. The remaining stellar fraction is a smooth function of the star formation efficiency, and depends on the distribution function of the stars. We calculate the fraction of stars remaining for this class of open cluster models and provide fitting formulae for representative cases.