THE STAR FORMATION RATE IN THE REIONIZATION ERA AS INDICATED BY GAMMA-RAY BURSTS

High-redshift gamma-ray bursts (GRBs) offer an extraordinary opportunity to study aspects of the early universe, including the cosmic star formation rate (SFR). Motivated by the two recent highest-z GRBs, GRB 080913 at z similar or equal to 6.7 and GRB 090423 at z similar or equal to 8.1, and more than four years of Swift observations, we first confirm that the GRB rate does not trace the SFR in an unbiased way. Correcting for this, we find that the implied SFR to beyond z = 8 is consistent with Lyman Break Galaxy-based measurements after accounting for unseen galaxies at the faint end of the UV luminosity function. We show that this provides support for the integrated star formation in the range 6 less than or similar to z less than or similar to 8 to have been alone sufficient to reionize the universe.