Core dissolution and the dynamics of massive stars in young stellar clusters

We investigate the dynamical effects of rapid gag expulsion from the core of a young stellar cluster. The aims of this study are to determine (i) whether a mass-segregated core survives the gas expulsion and (ii) the probable location of any massive stars that have escaped from the core. Feedback from massive stars is expected to remove the gas from the core of the cluster first, as that is where most massive stars are located. We find that gas expulsion has little effect on the core for a core star formation efficiency, epsilon, of greater than 50 per cent. For lower values of epsilon down to 20 per cent, a reduced core survives containing the majority of the massive stars while some of them are dispersed into the rest of the cluster. In fact, we find that ejected stars migrate from radial to tangential orbits due to stellar encounters once they leave the core. Thus, the location of massive stars outside of the core does not exclude their forming in the dense cluster core. Few massive stars are expected to remain in the core for epsilon lower than 20 per cent.