Galaxies at redshifts 5 to 6 with systematically low dust content and high [C II] emission

Capak, Peter L. and Carilli, C. and Jones, G. and Casey, C. M. and Riechers, D. and Sheth, K. and Carollo, C. M. and Ilbert, O. and Karim, A. and LeFevre, O. and Lilly, S. and Scoville, N. and Smolčić, Vernesa and Yan, L. (2015) Galaxies at redshifts 5 to 6 with systematically low dust content and high [C II] emission. Nature, 522. pp. 455-458. ISSN 0028-0836 (Submitted)

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The rest-frame ultraviolet properties of galaxies during the first three billion years of cosmic time (redshift z > 4) indicate a rapid evolution in the dust obscuration of such galaxies. This evolution implies a change in the average properties of the interstellar medium, but the measurements are systematically uncertain owing to untested assumptions and the inability to detect heavily obscured regions of the galaxies. Previous attempts to measure the interstellar medium directly in normal galaxies at these redshifts have failed for a number of reasons, with two notable exceptions. Here we report measurements of the forbidden C II emission (that is, [C II]) from gas, and the far-infrared emission from dust, in nine typical star-forming galaxies about one billion years after the Big Bang (z ~ 5-6). We find that these galaxies have thermal emission that is less than 1/12 that of similar systems about two billion years later, and enhanced [C II] emission relative to the far-infrared continuum, confirming a strong evolution in the properties of the interstellar medium in the early Universe. The gas is distributed over scales of one to eight kiloparsecs, and shows diverse dynamics within the sample. These results are consistent with early galaxies having significantly less dust than typical galaxies seen at z < 3 and being comparable in dust content to local low-metallicity systems.

Item Type: Article
Date: 25 June 2015
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2015 Nature Publishing Group. Received 20 November 2014. Accepted 23 April 2015. Published online 24 June 2015.
Divisions: Faculty of Science > Department of Physics
Publisher: Nature Publishing Group
Depositing User: Vernesa Smolčić
Date Deposited: 09 May 2016 09:48
Last Modified: 09 May 2016 09:48

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