Abstrakt
The mass function of freshly formed star clusters is empirically often described as a power law. However, the cluster mass function of populations of young clusters over the scale of a galaxy has been found to be described by a Schechter-function.
Here we address this apparent discrepancy. We assume that in an annulus of an isolated self-regulated radially exponential axially symmetric disc galaxy, the local mass function of very young (embedded) clusters is a power law with an upper mass limit which depends on the local star formation rate density.
Radial integration of this mass function yields a galaxy-wide embedded cluster mass function. This integrated embedded cluster mass function has a Schechter-type form, which results from the addition of many low-mass clusters forming at all galactocentric distances and rarer massive clusters only forming close to the centre of the galaxy.