The local environments of long-duration gamma-ray bursts

We construct various properties (e.g., metallicity/redshift distributions) for populations of long-duration gammaray bursts (GRBs) from different proposed progenitor models. We use a description of star formation that takes into account the evolution of metallicity with redshift and galaxy mass, the evolution of galaxy mass with redshift, and the star formation rate with galaxy mass and redshift. We compare predicted distributions with redshift and metallicity to observations of GRB host galaxies and find that the simple models cannot produce the observed distributions, but that current theoretical models can reproduce the observations within some constraints on the fraction of fallback black holes that produce GRBs.