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Abstract: Abridged The dynamical ejection of stars from star clusters affects theshape of the stellar mass function MF in these clusters, because the escapeprobability of a star depends on its mass. The objective of this paper is toprovide and to apply a simple physical model for the evolution of the MF instar clusters for a large range of the parameter space. The model is derivedfrom the basic principles of two-body encounters and energy considerations. Itis independent of the adopted mass loss rate or initial mass function IMF,and contains stellar evolution, stellar remnant retention, dynamicaldissolution in a tidal field, and mass segregation. It is found that the MFevolution in star clusters depends on the disruption time, remnant retentionfraction, initial-final stellar mass relation, and IMF. Low-mass stars arepreferentially ejected after t~400 Myr. Before that time, masses around 15-20%of the maximum stellar mass are lost. The degree of low-mass star depletiongrows for increasing disruption times, but can be quenched when the retainedfraction of massive remnants is large. The highly depleted MFs of certainGalactic globular clusters are explained by the enhanced low-mass stardepletion that occurs for low remnant retention fractions. Unless the retentionfraction is exceptionally large, dynamical evolution always decreases themass-to-light ratio. The modeled evolution of the MF is consistent with N-bodysimulations when adopting identical boundary conditions. However, it is foundthat the results from N-body simulations only hold for their specific boundaryconditions and should not be generalised to all clusters. It is concluded thatthe model provides an efficient method do understand the evolution of thestellar MF in star clusters under widely varying conditions.

Author: J. M. Diederik Kruijssen



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