A dusty, normal galaxy in the epoch of reionization
Journal
Date Issued
2015
Author(s)
Watson, Darach
•
Christensen, Lise
•
Knudsen, Kirsten Kraiberg
•
Richard, Johan
•
•
Michałowski, Michał Jerzy
Description
The Dark Cosmology Centre is funded by the Danish National Research Foundation. L.C. is supported by the EU under a Marie Curie Intra-European Fellowship, contract number PIEF-GA-2010-274117. K.K. acknowledges support from the Swedish Research Council and the Knut and Alice Wallenberg Foundation. J.R. acknowledges support from a European Research Council starting grant, CALENDS, and the Career Integration Grant 294074. A.G. acknowledges support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 267251 (“AstroFIt”). M.J.M. acknowledges the support of the Science and Technology Facilities Council. ALMA is a partnership of the European Southern Observatory (ESO, representing its member states), the National Science Foundation (USA) and National Institutes of Natural Sciences (Japan), together with the National Research Council (Canada) and the National Science Council and the Academia Sinica Institute for Astronomy and Astrophysics (Taiwan), in cooperation with Chile. The Joint ALMA Observatory is operated by the ESO, Associated Universities Inc./National Radio Astronomy Observatory and the National Astronomical Observatory of Japan. We thank L. Lindroos, J. Hjorth, J. Fynbo, A. C. Andersen, and R. Bouwens for discussions, M. Limousin for providing a lensing map of the cluster, and the Nordic ALMA Regional Center Node for assistance.
Abstract
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 (ref. 5), 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-zD1. 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-α 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.
Volume
519
Issue
7543
Start page
327
Issn Identifier
0028-0836
Ads BibCode
2015Natur.519..327W
Rights
open.access
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