Competitive accretion in embedded stellar clusters

We investigate the physics of gas accretion in young stellar clusters. Accr etion in clusters is a dynamic phenomenon as both the stars and the gas res pond to the same gravitational potential. Accretion rates are highly non-un iform with stars nearer the centre of the cluster, where gas densities are higher, accreting more than others. This competitive accretion naturally re sults in both initial mass segregation and a spectrum of stellar masses. Ac cretion in gas-dominated clusters is well modelled using a tidal-lobe radiu s instead of the commonly used Bondi-Hoyle accretion radius. This works as both the stellar and gas velocities are under the influence of the same gra vitational potential and are thus comparable. The low relative velocity whi ch results means that R-tidal < R-BH in these systems. In contrast, when th e stars dominate the potential and are virialized, R-BH < R-tidal and Bondi -Hoyle accretion is a better fit to the accretion rates.