Gamma-ray burst host galaxy surveys at redshift z ≳ 4: Probes of star formation rate and cosmic reionization

Abstract

Measuring the star formation rate (SFR) at high redshift is crucial for understanding cosmic reionization and galaxy formation. Two common complementary approaches are Lyman break galaxy (LBG) surveys for large samples and gamma-ray burst (GRB) observations for sensitivity to SFR in small galaxies. The z ≳ 4 GRB-inferred SFR is higher than the LBG rate, but this difference is difficult to understand, as both methods rely on several modeling assumptions. Using a physically motivated galaxy luminosity function model, with star formation in dark matter halos with virial temperature T vir ≳ 2 × 104 K (M DM ≳ 2 × 108 M ⊙), we show that GRB- and LBG-derived SFRs are consistent if GRBs extend to fa..