Radiation-driven collapse of autogravitating neutral clumps

We present three-dimensional (3D) simulations of the interaction of autogravitating neutral clumps with an external ionizing radiation field. We used gas-dynamics simulations that included self-gravity and the divergence of the radiation from the source. We show that as a spherical neutral clump is being photoevaporated, a compressive shock is established, the shape of which depends upon the distance to the source. For a clump with small density perturbations, we found evidence of further fragmentation when the photon source is placed very near to the clump. We also found that self-gravity has a secondary role unless very high densities are achieved by the initial radiation-driven compression.