ON THE FORMATION OF MASSIVE STARS

We present a model for the formation of massive (M greater than or sim ilar to 10 M-.) stars through accretion-induced collisions in the core s of embedded dense stellar clusters. This model circumvents the probl em of accreting on to a star whose luminosity is sufficient to reverse the infall of gas. Instead, the central core of the cluster accretes from the surrounding gas, thereby decreasing its radius until collisio ns between individual components become sufficient. These components a re, in general, intermediate-mass stars that have formed through accre tion on to low-mass protostars. Once a sufficiently massive star has f ormed to expel the remaining gas, the cluster expands in accordance wi th this loss of mass, halting further collisions. This process implies a critical stellar density for the formation of massive stars, and a high rate of binaries formed by tidal capture.