Determining the escape fraction of ionizing photons during reionization with the GRB-derived star formation rate

Abstract

The fraction of ionizing photons that escape their host galaxies and so are able to ionize hydrogen in the inter-galactic medium (IGM) is a critical parameter in the analyses of the reionization era and early galaxy formation. Studies of the reionization history normally suffer from a degeneracy between the unknown values for the efficiency with which high-redshift galaxies turn mass into stars and the escape fraction of ionizing photons. Recent gamma-ray burst (GRB) measurements of the star formation rate density during reionization provide the first opportunity to break this degeneracy. We confront a semi-analytic model for reionization with the GRB-derived star formation rate, as well as ..