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We highlight the impact of cluster‐mass‐dependent evolutionary rates upon the evolution of the cluster mass function during violent relaxation, that is, while clusters dynamically respond to the expulsion of their residual star‐forming gas. Mass‐dependent evolutionary rates arise when the mean volume density of cluster‐forming regions is mass‐dependent. In that case, even if the initial conditions are such that the cluster mass function at the end of violent relaxation has the same shape as the embedded‐cluster mass function (i.e. infant weight‐loss is mass‐independent), the shape of the cluster mass function does change transiently  during  violent relaxation. In contrast, for cluster‐forming regions of constant mean volume density, the cluster mass function shape is preserved all through violent relaxation since all clusters then evolve at the same mass‐independent rate.  On the scale of individual clusters, we model the evolution of the ratio of the dynamical mass to luminous mass of a cluster after gas expulsion. Specifically, we map the radial dependence of the time‐scale for a star cluster to return to equilibrium. We stress that fields of view a few pc in size only, typical of compact clusters with rapid evolutionary rates, are likely to reveal cluster regions which have returned to equilibrium even if the cluster experienced a major gas expulsion episode a few Myr earlier. We provide models with the aperture and time expressed in units of the initial half‐mass radius and initial crossing‐time, respectively, so that our results can be applied to clusters with initial densities, sizes, and apertures different from ours.

The mass function and dynamical mass of young star clusters: why their initial crossing‐time matters crucially