Mass Limits For Black Hole Formation

We present a series of two-dimensional core-collapse supernova simulations for a range of progenitor masses and different input physics. These models predict a range of supernova energies and compact remnant masses. In particular, we study two mechanisms for black hole formation: prompt collapse and delayed collapse due to fallback. For massive progenitors (20M ⊙), after a hydrodynamic time for the helium core (a few minutes to a few hours), fallback drives the compact object beyond the maximum neutron star mass causing it to collapse into a black hole. With the current accuracy of the models, progenitors more massive than 40M ⊙ form black holes directly with no supernova explosion (if rotating, these black holes may be the progenitors of gamma-ray bursts). We calculate the mass distribution of black holes formed, and compare these predictions to the observations, which represent a small biased subset of the black hole population. Uncertainties in these estimates are discussed.