Simulated distribution of cluster mass as a function of the cluster bolometric luminosities at birth. The large filled circles show the average cluster mass in each bolometric luminosity bin. The broken dashed line is a fit to the average log M − log L_bol relation: at high luminosities it follows the linear relation between mass and luminosity expected for a fully populated IMF, while for log L_bol < 3 × 10³⁹ erg s^-1 it approximates well the simulation results.