A dusty, normal galaxy in the epoch of reionization
Journal article, 2015

Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z> 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2, and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z >= 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zDI. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 +/- 0.2 from a spectroscopic detection of the Lyman-a break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z> 7.

Molecular Gas

Local Universe

High-Redshift Galaxies

Lyman Break

Similar-To 7


Submillimeter Galaxies


Star-Forming Galaxies

Starburst Galaxy



D. Watson

Niels Bohr Institute

L. Christensen

Niels Bohr Institute

Kirsten Kraiberg Knudsen

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

J. Richard

Université de Lyon

A. Gallazzi

Niels Bohr Institute

Istituto nazionale di astrofisica (INAF)

M. J. Michalowski

University of Edinburgh


0028-0836 (ISSN) 1476-4687 (eISSN)

Vol. 519 7543 327-330

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences



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