ACCRETION AND THE STELLAR MASS-SPECTRUM IN SMALL CLUSTERS

We investigate the effects of gas accretion on small clusters of young stars. The evolution of clusters containing 3-10 stars and between 0. 1 and 90 per cent of their masses in the form of gas is followed using a three-dimensional SPH code with sink-particles to treat the accreti on of gas on to the stars. The gas accretion by the stars is highly no n-uniform in that a few of the stars accrete significantly more than t he rest. The location of the star in the cluster potential and its pos sible membership in a binary or multiple system are the primary factor s in determining the accretion rate of the star. This competitive accr etion process results in the formation of a spectrum of stellar masses , even when the initial stellar masses are uniform. Small variations i n the initial masses are overwhelmed by the accretion process, whereas larger variations can affect the accretion dynamics as they affect th e overall cluster potential. The differential accretion results in the massive stars being formed in the centre of the cluster. Their locati on is not due to an evolutionary effect of mass segregation. Implicati ons of this competitive accretion process for determining the stellar mass spectrum are discussed.