Talk abstract

The observed slope at the high-mass end of the initial mass function (IMF) displays a remarkable universality under a wide-variety of physical environments. We will present results from numerical simulations that cover a wide range of metallicities and environmental conditions, that demonstrate that the process of competitive accretion can provide a natural explanation for a universal slope in the IMF. In our discussion, we show how competitive accretion always dominates over the more traditional 'fragmentation' picture wherever star formation occurs in bound clusters. Further, we argue that clustered star formation has been the dominant mode of star formation, throughout cosmic time, dominating even the formation of the very first stars in the Universe -- the so called Population III stars. We also discuss the ability of other physical processes to lessen the effects of further accretion onto protostellar cores. Current theoretical and numerical studies show that competitive accretion is robust against disrupting effects -- such as feed-back from young stars, supersonic turbulence and magnetic fields -- in all but the most extreme cases.