Matt Kistler homepage. Matthew Kistler Revealing the High-Redshift Star Formation Rate with Gamma-Ray Bursts
Can stars account for cosmic reionization?
It still remains an open question as to what objects reionized the universe. It seems as if quasars can not do the job, but it is hard to observe galaxies directly to determine whether stars could have been responsible. This paper, completed with Hasan Yuksel, John Beacom, and Andrew Hopkins, using recent high-z observations of Swift gamma-ray bursts to make a new determination of the star formation rate at z = 4-7. Our results exceed the lowest direct star formation rate measurements, implying that no steep drop exists in the SFR up to at least z ~ 6.5. Discussed are the implications of our measurement for reionization, the apparent increase in the efficiency of the universe in producing stellar-mass black holes in its earlier history, and the possibility of ``GRB feedback'' in their small, star-forming hosts.
