A galaxy at a redshift z=6.96
A galaxy at a redshift z=6.96
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DOI：
10.1038/nature05104
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发表时间：
2006-09-14
期刊：
影响因子：
64.8
通讯作者：
Shimasaku, Kazuhiro
中科院分区：
文献类型：
--
作者：
Iye, Masanori;Ota, Kazuaki;Shimasaku, Kazuhiro
宇宙历史中星系形成的开始时间仍不清楚。对宇宙微波背景的研究表明，宇宙在最初冷却后（大爆炸之后），被新生星系中的热恒星在 6 < z < 14 范围内的红移范围内重新加热和再电离（参考文献 1）。尽管已经通过光度测定确定了几个红移 z > 7 的候选星系(2,3)，但经光谱证实红移的星系仅限于 z < 6.6（参考文献 4 - 8）。在这里，我们报告了一个星系的光谱红移 z = 6.96（相当于大爆炸后仅 750 Myr），该星系的光谱清楚地显示了 9,682 埃处的莱曼-α 发射，表明活跃恒星形成的速率类似于 10M(.) yr(-1)，其中 M-.是太阳的质量。这表明，当宇宙年龄仅为当前年龄的 6% 时，星系正在形成。 z 接近 7 处的星系数密度似乎仅为 z = 6.6 处的密度的 18 - 36%。
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(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 angstrom, indicating active star formation at a rate of similar to 10M(.) yr(-1), where M-. is the mass of the Sun. This demonstrates that galaxy formation was under way when the Universe was only similar to 6 per cent of its present age. The number density of galaxies at z approximate to 7 seems to be only 18 - 36 per cent of the density at z = 6.6.