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 (refs 2,3), 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 about 10 M_sun/yr, where M_sun us the mass of the Sun. This demonstrates that galaxy formation was under way when the Universe was only about 6 per cent of its present age. The number density of galaxies at z = 7 seems to be only 18-36 per cent of the density at z = 6.6.
Keywords
Cite
@article{arxiv.astro-ph/0609393,
title = {A galaxy at a redshift z = 6.96},
author = {Masanori Iye and Kazuaki Ota and Nobunari Kashikawa and Hisanori Furusawa and Tetsuya Hashimoto and Takashi Hattori and Yuichi Matsuda and Tomoki Morokuma and Masami Ouchi and Kazuhiro Shimasaku},
journal= {arXiv preprint arXiv:astro-ph/0609393},
year = {2009}
}
Comments
10 pages, 3 figure, 1 table