title: A photometric redshift of z = 6.39 +/- 0.12 for GRB 050904.
abstract: Gamma-ray bursts (GRBs) and their afterglows are the most brilliant transient events in the Universe. Both the bursts themselves and their afterglows have been predicted to be visible out to redshifts of z approximately 20, and therefore to be powerful probes of the early Universe. The burst GRB 000131, at z = 4.50, was hitherto the most distant such event identified. Here we report the discovery of the bright near-infrared afterglow of GRB 050904 (ref. 4). From our measurements of the near-infrared afterglow, and our failure to detect the optical afterglow, we determine the photometric redshift of the burst to be z = 6.39 - 0.12 + 0.11 (refs 5-7). Subsequently, it was measured spectroscopically to be z = 6.29 +/- 0.01, in agreement with our photometric estimate. These results demonstrate that GRBs can be used to trace the star formation, metallicity, and reionization histories of the early Universe.
authors.affiliation: Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Campus Box 3255, Chapel Hill, North Carolina 27599, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Haislip
authors.forename: M C
authors.initials: MC
authors.lastname: Nysewander
authors.forename: D E
authors.initials: DE
authors.lastname: Reichart
authors.forename: A
authors.initials: A
authors.lastname: Levan
authors.forename: N
authors.initials: N
authors.lastname: Tanvir
authors.forename: S B
authors.initials: SB
authors.lastname: Cenko
authors.forename: D B
authors.initials: DB
authors.lastname: Fox
authors.forename: P A
authors.initials: PA
authors.lastname: Price
authors.forename: A J
authors.initials: AJ
authors.lastname: Castro-Tirado
authors.forename: J
authors.initials: J
authors.lastname: Gorosabel
authors.forename: C R
authors.initials: CR
authors.lastname: Evans
authors.forename: E
authors.initials: E
authors.lastname: Figueredo
authors.forename: C L
authors.initials: CL
authors.lastname: MacLeod
authors.forename: J R
authors.initials: JR
authors.lastname: Kirschbrown
authors.forename: M
authors.initials: M
authors.lastname: Jelinek
authors.forename: S
authors.initials: S
authors.lastname: Guziy
authors.forename: A
authors.initials: A
authors.lastname: de Ugarte Postigo
authors.forename: E S
authors.initials: ES
authors.lastname: Cypriano
authors.forename: A
authors.initials: A
authors.lastname: LaCluyze
authors.forename: J
authors.initials: J
authors.lastname: Graham
authors.forename: R
authors.initials: R
authors.lastname: Priddey
authors.forename: R
authors.initials: R
authors.lastname: Chapman
authors.forename: J
authors.initials: J
authors.lastname: Rhoads
authors.forename: A S
authors.initials: AS
authors.lastname: Fruchter
authors.forename: D Q
authors.initials: DQ
authors.lastname: Lamb
authors.forename: C
authors.initials: C
authors.lastname: Kouveliotou
authors.forename: R A M J
authors.initials: RA
authors.lastname: Wijers
authors.forename: M B
authors.initials: MB
authors.lastname: Bayliss
authors.forename: B P
authors.initials: BP
authors.lastname: Schmidt
authors.forename: A M
authors.initials: AM
authors.lastname: Soderberg
authors.forename: S R
authors.initials: SR
authors.lastname: Kulkarni
authors.forename: F A
authors.initials: FA
authors.lastname: Harrison
authors.forename: D S
authors.initials: DS
authors.lastname: Moon
authors.forename: A
authors.initials: A
authors.lastname: Gal-Yam
authors.forename: M M
authors.initials: MM
authors.lastname: Kasliwal
authors.forename: R
authors.initials: R
authors.lastname: Hudec
authors.forename: S
authors.initials: S
authors.lastname: Vitek
authors.forename: P
authors.initials: P
authors.lastname: Kubanek
authors.forename: J A
authors.initials: JA
authors.lastname: Crain
authors.forename: A C
authors.initials: AC
authors.lastname: Foster
authors.forename: J C
authors.initials: JC
authors.lastname: Clemens
authors.forename: J W
authors.initials: JW
authors.lastname: Bartelme
authors.forename: R
authors.initials: R
authors.lastname: Canterna
authors.forename: D H
authors.initials: DH
authors.lastname: Hartmann
authors.forename: A A
authors.initials: AA
authors.lastname: Henden
authors.forename: S
authors.initials: S
authors.lastname: Klose
authors.forename: H-S
authors.initials: HS
authors.lastname: Park
authors.forename: G G
authors.initials: GG
authors.lastname: Williams
authors.forename: E
authors.initials: E
authors.lastname: Rol
authors.forename: P
authors.initials: P
authors.lastname: O'Brien
authors.forename: D
authors.initials: D
authors.lastname: Bersier
authors.forename: F
authors.initials: F
authors.lastname: Prada
authors.forename: S
authors.initials: S
authors.lastname: Pizarro
authors.forename: D
authors.initials: D
authors.lastname: Maturana
authors.forename: P
authors.initials: P
authors.lastname: Ugarte
authors.forename: A
authors.initials: A
authors.lastname: Alvarez
authors.forename: A J M
authors.initials: AJ
authors.lastname: Fernandez
authors.forename: M J
authors.initials: MJ
authors.lastname: Jarvis
authors.forename: M
authors.initials: M
authors.lastname: Moles
authors.forename: E
authors.initials: E
authors.lastname: Alfaro
authors.forename: K M
authors.initials: KM
authors.lastname: Ivarsen
authors.forename: N D
authors.initials: ND
authors.lastname: Kumar
authors.forename: C E
authors.initials: CE
authors.lastname: Mack
authors.forename: C M
authors.initials: CM
authors.lastname: Zdarowicz
authors.forename: N
authors.initials: N
authors.lastname: Gehrels
authors.forename: S
authors.initials: S
authors.lastname: Barthelmy
authors.forename: D N
authors.initials: DN
authors.lastname: Burrows