The Virtual Observatory as a Tool to Study Star Cluster Populations in Starburst Galaxies

The cluster luminosity function (CLF) is one of the most important diagnostics in the study of old globular and young compact star cluster populations. While the CLFs of young star cluster systems are closely approximated by power laws, as predicted by standard cluster formation models (e.g., [2] [4]), for old globular cluster systems the shape of the CLF, and also of the initial mass function, is well-established to be roughly Gaussian, with an apparently universal turnover luminosity (mass). Processes responsible for the transformation of the CLF of young star cluster systems into the lognormal distributions characteristic of older CLFs include differential fading due to aging of the cluster population, the preferential depletion of low-mass clusters by evaporation and tidal interaction with the gravitational field of the parent galaxy, and the preferential destruction of high-masss clusters by dynamical friction. The relative importance of these destruction processes is still controversial (see, e.g., [4] [5] [6]). One should be cautious, however, to generalize any of the “standard” models, since they only apply to quiescent, non-interacting galaxies. In the high-pressure environments and the time-varying potentials of interacting and merging galaxies we expect significant differences for the cluster formation and destruction processes, mass spectra, and time-scales for the dynamical evolution of star clusters due to, e.g., external pressure and shocks.