Gas expulsion versus gas retention: what process dominates in young massive clusters?

Gas expulsion and the destruction of massive young clusters

We examine the luminosity and dynamical mass estimates for young massive stellar clusters. For many young (< 50 Myr) clusters, the luminosity and dynamical mass estimates differ by a significant amount. We explain this as being due to many young clusters being out of virial equilibrium (which is assumed in dynamical mass estimates) because the clusters are undergoing violent relaxation after ex...

Gas expulsion in massive star clusters?

Context. Gas expulsion is a central concept in some of the models for multiple populations and the light-element anti-correlations in globular clusters. If the star formation efficiency was around 30 per cent and the gas expulsion happened on the crossing timescale, this process could preferentially expel stars born with the chemical composition of the proto-cluster gas, while stars with specia...

Residual gas expulsion from young globular clusters

The results of N -body simulations of the effects of the expulsion of residual gas (that gas not used in star formation) from very young globular clusters is presented. Globular clusters of a variety of initial masses, Galactocentric radii, concentration and initial mass function slope with star formation efficiencies of < ∼ 50% were simulated. The residual gas was expelled by the action of mas...

Gas Dynamics in Clusters

The effect of the dynamical state of clusters on gas expulsion and infant mortality

The star formation efficiency (SFE) of a star cluster is thought to be the critical factor in determining if the cluster can survive for a significant (> 50 Myr) time. There is an often quoted critical SFE of ∼ 30 per cent for a cluster to survive gas expulsion. I reiterate that the SFE is not the critical factor, rather it is the dynamical state of the stars (as measured by their virial ratio)...