Model predictions for GRB host galaxies

To investigate this correlation, we use a phenomenological model that successfully describes star formation rates, luminosities, and stellar masses of star-forming galaxies and apply it to GRB production. We predict the luminosities, stellar masses, and metallicities of host galaxies depending on the presence (or absence) of a metallicity bias.

Our best-fitting model includes a moderate metallicity bias, broadly consistent with the large majority of the long-duration GRBs in metal-poor environments originating from a collapsar (probability ~83%, with [0.74;0.91] range at 90% confidence level), but with a secondary contribution (~17%) from a metal-independent production channel, such as binary evolution. Because of the mass-metallicity relation of galaxies, the maximum likelihood model predicts that the metal-independent channel becomes dominant at z~<2, where hosts have higher metallicities and collapsars are suppressed.