A dusty, normal galaxy in the epoch of reionization

TY - JOUR

T1 - A dusty, normal galaxy in the epoch of reionization

AU - Watson, Darach

AU - Christensen, Lise

AU - Knudsen, Kirsten Kraiberg

AU - Richard, Johan

AU - Gallazzi, Anna

AU - Michałowski, Michał Jerzy

N1 - Nature in press. 14 pages, 10 figures, including methods section

PY - 2015/3/19

Y1 - 2015/3/19

N2 - 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 imaging1. But it has proved difficult for existingspectrographs to characterize themusing their ultraviolet light2-4. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have becomesufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dustemission is only at z53 >2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z > 76-8. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1.Wedetect its stellar continuum in spectroscopy and determine its redshift to be z 57.560.2 from a spectroscopic detection of the Lyman-a break. A1689-zD1 is representative of the star-forming population during the epoch of reionization9, with a total star-formation rate of about 12 solarmasses 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.

AB - 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 imaging1. But it has proved difficult for existingspectrographs to characterize themusing their ultraviolet light2-4. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have becomesufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dustemission is only at z53 >2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z > 76-8. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1.Wedetect its stellar continuum in spectroscopy and determine its redshift to be z 57.560.2 from a spectroscopic detection of the Lyman-a break. A1689-zD1 is representative of the star-forming population during the epoch of reionization9, with a total star-formation rate of about 12 solarmasses 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.

KW - astro-ph.GA

U2 - 10.1038/nature14164

DO - 10.1038/nature14164

M3 - Journal article

C2 - 25731171

SN - 0028-0836

VL - 519

SP - 327

EP - 330

JO - Nature

JF - Nature

ER -