A galaxy rapidly forming stars 700 million years after the Big Bang at redshift 7.51

• Published in: Nature (London) Vol. 502; no. 7472; pp. 524 - 527
• Main Authors: Finkelstein, S. L., Papovich, C., Dickinson, M., Song, M., Tilvi, V., Koekemoer, A. M., Finkelstein, K. D., Mobasher, B., Ferguson, H. C., Giavalisco, M., Reddy, N., Ashby, M. L. N., Dekel, A., Fazio, G. G., Fontana, A., Grogin, N. A., Huang, J.-S., Kocevski, D., Rafelski, M., Weiner, B. J., Willner, S. P.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.10.2013; Nature Publishing Group
• Subjects: 639/33/34/124; 639/33/34/863; Big bang theory; Cosmic physics; Humanities and Social Sciences; letter; multidisciplinary; Red shift; Science; United States
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature12657

A deep near-infrared spectroscopic survey of 43 photometrically-selected galaxies with redshift z  > 6.5 detects a near-infrared emission line from only a single galaxy; this line is likely to be Lyman α emission at a wavelength of 1.0343 μm, placing this galaxy at z = 7.51. Most distant star-forming galaxy confirmed Hubble Space Telescope data have yielded hundreds of candidates for galaxies with redshifts observed less than one billion years from the Big Bang, but so far distances have been confirmed for only a few of them. Using the newly commissioned MOSFIRE spectrograph on the Keck I telescope, Steven Finkelstein and co-workers have detected a galaxy with an emission line that can be confirmed at a redshift of 7.51, placing it at an epoch 700 million years after the Big Bang. That makes it the most distant spectroscopically confirmed galaxy, This galaxy's colours are consistent with a significant metal content, and it has a surprisingly high star-formation rate of about 330 solar masses per year, more than 100-fold greater than that seen in the Milky Way. The authors suggest that there may be many more such sites of intense star formation in the early Universe than previously expected. Of several dozen galaxies observed spectroscopically that are candidates for having a redshift ( z ) in excess of seven, only five have had their redshifts confirmed via Lyman α emission, at z = 7.008, 7.045, 7.109, 7.213 and 7.215 (refs 1 , 2 , 3 , 4 ). The small fraction of confirmed galaxies may indicate that the neutral fraction in the intergalactic medium rises quickly at z  > 6.5, given that Lyman α is resonantly scattered by neutral gas 3 , 5 , 6 , 7 , 8 . The small samples and limited depth of previous observations, however, makes these conclusions tentative. Here we report a deep near-infrared spectroscopic survey of 43 photometrically-selected galaxies with z  > 6.5. We detect a near-infrared emission line from only a single galaxy, confirming that some process is making Lyman α difficult to detect. The detected emission line at a wavelength of 1.0343 micrometres is likely to be Lyman α emission, placing this galaxy at a redshift z = 7.51, an epoch 700 million years after the Big Bang. This galaxy’s colours are consistent with significant metal content, implying that galaxies become enriched rapidly. We calculate a surprisingly high star-formation rate of about 330 solar masses per year, which is more than a factor of 100 greater than that seen in the Milky Way. Such a galaxy is unexpected in a survey of our size 9 , suggesting that the early Universe may harbour a larger number of intense sites of star formation than expected.