title: A galaxy at a redshift z = 6.96.
abstract: When galaxy formation started in the history of the Universe remains unclear. Studies of the cosmic microwave background indicate that the Universe, after initial cooling (following the Big Bang), was reheated and reionized by hot stars in newborn galaxies at a redshift in the range 6 < z < 14 (ref. 1). Though several candidate galaxies at redshift z > 7 have been identified photometrically, galaxies with spectroscopically confirmed redshifts have been confined to z < 6.6 (refs 4-8). Here we report a spectroscopic redshift of z = 6.96 (corresponding to just 750 Myr after the Big Bang) for a galaxy whose spectrum clearly shows Lyman-alpha emission at 9,682 A, indicating active star formation at a rate of approximately 10M(o) yr(-1), where M(o) is the mass of the Sun. This demonstrates that galaxy formation was under way when the Universe was only approximately 6 per cent of its present age. The number density of galaxies at z approximately 7 seems to be only 18-36 per cent of the density at z = 6.6.
authors.affiliation: National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan. iye@optik.mtk.nao.ac.jp
authors.forename: Masanori
authors.initials: M
authors.lastname: Iye
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Ota
authors.forename: Nobunari
authors.initials: N
authors.lastname: Kashikawa
authors.forename: Hisanori
authors.initials: H
authors.lastname: Furusawa
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Hattori
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Tomoki
authors.initials: T
authors.lastname: Morokuma
authors.forename: Masami
authors.initials: M
authors.lastname: Ouchi
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shimasaku