Journal Article

A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34

Hurley, P., Franceschini, A., Farrah, D., Page, M. J., Zemcov, M., Neri, R., Smith, A. J., Gavazzi, R., Hyde, A., Oliver, S. J., Scott, D., Ibar, E., Conley, A., Maloney, P. R., Ivison, R. J., Ferrero, P., Martinez-Navajas, P., Roseboom, I. G., Matsuhara, H., Clements, D. L., Valtchanov, I., Béthermin, M., Dunlop, J. S., Riechers, Dominik A., Cooray, A., Earle, L., Dowell, C. D., Arumugam, V., Gurwell, M. A., Pérez-Fournon, I., Viero, M., Hatziminaoglou, E., Omont, A., Bradford, C. M., Kovács, A., Wang, L., Halpern, M., Staguhn, J. G., Thomson, A. P., Vieira, J. D., Altieri, B., Benford, D. J., Chapman, S. C., Naylor, B. J., Rangwala, N., Streblyanska, A., Bock, J., Cox, P., Nguyen, H. T., Zmuidzinas, J., Cabrera-Lavers, A., Murphy, E. J., Kamenetzky, J., Bridge, C., Krips, M., Solares, E. A. Gonzalez, Wardlow, J., Burgarella, D., Aguirre, J. E., Fu, Hai, Petitpas, G., Calanog, J., Lupu, R. E., Glenn, J.

2013

Overview

A massive starburst galaxy with 100 billion solar masses of gas is identified at a redshift of 6.34; a ‘maximum starburst’ converts the gas into stars at a rate more than 2,000 times that of the Milky Way. A massive starburst galaxy unveiled The physical properties of the first massive starburst galaxies in the Universe provide important clues as to patterns of early cosmic structure formation. But as regions of intense star formation tend to be shrouded in dust, the search for such systems at very high redshift has been a major challenge. Now a massive starburst galaxy has been identified at a redshift z = 6.34, just 880 million years after the Big Bang when the Universe was one-sixteenth of its present age. Line-emission data reveal the presence of 100 billion solar masses of gas, equivalent to at least 40% of the galaxy's baryonic (visible matter) mass. The galaxy hosts an intense starburst, converting gas into stars at a rate more than 2,000 times that of the Milky Way. These findings are consistent with the theory that massive galaxies form via extreme starbursts in the early Universe. Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts—that is, increased rates of star formation—in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift ( z ) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects 1 , as confirmed by recent findings of systems with redshifts as high as ∼5 (refs 2–4 ). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A ‘maximum starburst’ converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts 5 , it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/766/33/34/863 / Analysis / Astrophysics / Big bang theory / Dust / High Energy Astrophysical Phenomena / Humanities and Social Sciences / letter / multidisciplinary / Observations / Physics / Population / Science / Sciences of the Universe / Solar and Stellar Astrophysics / Star & galaxy formation / Starburst galaxies / Stars / Stars & galaxies