title: Observations of GRBs at high redshift.
abstract: The extreme luminosity of gamma-ray bursts and their afterglows means they are detectable, in principle, to very high redshifts. Although the redshift distribution of gamma-ray bursts (GRBs) is difficult to determine, due to incompleteness of present samples, we argue that for Swift-detected bursts, the median redshift is between 2.5 and 3, with a few per cent probably at z>6. Thus, GRBs are potentially powerful probes of the era of reionization and the sources responsible for it. Moreover, it seems probable that they can provide constraints on the star-formation history of the Universe and may also help in the determination of the cosmological parameters.
authors.affiliation: Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK. nrt3@star.le.ac.uk
authors.forename: Nial R
authors.initials: NR
authors.lastname: Tanvir
authors.forename: Páll
authors.initials: P
authors.lastname: Jakobsson