The early evolution of the star cluster mass function

Several recent Studies have shown that the Star cluster initial Mass function (CIMF) call be well approximated by a power law, with indication,, for a steepening Or truncation at high masses. This contribution considers the evolution of such it mass function due to cluster disruption, with emphasis oil the part of the mass function that is observable in the first similar to 1 Gyr. A Schechter type function is used for the CIMF, with a power-law index of -2 at low masses and an exponential truncation at M(*). Cluster disruption due to the tidal field of the host galaxy and encounters with giant Molecular Clouds flattens the low-mass end of the mass function, but there is always a part of the 'evolved Schechter function' that can be approximated by a power law with index -2. The mass range for which this holds depends oil age, tau, and shifts to hi-her masses roughly as tau(0.6). Mean cluster masses derived front luminosity-limited samples increase with age very similarly due to the evolutionary fading of clusters.. Empirical mass functions are, therefore, approximately power laws with index -2. or slightly steeper. at all ages. The results are illustrated by all application to the star cluster population Of the interacting galaxy M51. which can be we] I described by a model with M(*) = (1.9 +/- 0.5) x 10(5) M(circle dot) and a short (mass-dependent) disruption time destroying M(*) Clusters in roughly a Gyr.