Normal, dust-obscured galaxies in the epoch of reionization

Y Fudamoto; P A Oesch; S Schouws; M Stefanon; R Smit; R J Bouwens; R A A Bowler; R Endsley; V Gonzalez; H Inami; I Labbe; D Stark; M Aravena; L Barrufet; E da Cunha; P Dayal; A Ferrara; L Graziani; J Hodge; A Hutter; Y Li; I De Looze; T Nanayakkara; A Pallottini; D Riechers; R Schneider; G Ucci; P van der Werf; C White

doi:10.1038/s41586-021-03846-z

Normal, dust-obscured galaxies in the epoch of reionization

Nature. 2021 Sep;597(7877):489-492. doi: 10.1038/s41586-021-03846-z. Epub 2021 Sep 22.

Authors

Y Fudamoto^{1

2

3}, P A Oesch^{4

5}, S Schouws⁶, M Stefanon⁶, R Smit⁷, R J Bouwens⁶, R A A Bowler⁸, R Endsley⁹, V Gonzalez^{10

11}, H Inami¹², I Labbe¹³, D Stark⁹, M Aravena¹⁴, L Barrufet⁴, E da Cunha^{15

16}, P Dayal¹⁷, A Ferrara¹⁸, L Graziani^{19

20

21}, J Hodge⁶, A Hutter¹⁷, Y Li^{22

23}, I De Looze^{24

25}, T Nanayakkara¹³, A Pallottini¹⁸, D Riechers²⁶, R Schneider^{19

27

28

21}, G Ucci¹⁷, P van der Werf⁶, C White⁹

Affiliations

¹ Department of Astronomy, University of Geneva, Versoix, Switzerland. yoshinobu.fudamoto@gmail.com.
² Research Institute for Science and Engineering, Waseda University, Shinjuku, Tokyo, Japan. yoshinobu.fudamoto@gmail.com.
³ National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan. yoshinobu.fudamoto@gmail.com.
⁴ Department of Astronomy, University of Geneva, Versoix, Switzerland.
⁵ Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, København, Denmark.
⁶ Leiden Observatory, Leiden University, Leiden, the Netherlands.
⁷ Astrophysics Research Institute, Liverpool John Moores University, Liverpool, UK.
⁸ Sub-department of Astrophysics, The Denys Wilkinson Building, University of Oxford, Oxford, UK.
⁹ Steward Observatory, University of Arizona, Tucson, AZ, USA.
¹⁰ Departmento de Astronomia, Universidad de Chile, Santiago, Chile.
¹¹ Centro de Astrofisica y Tecnologias Afines (CATA), Santiago, Chile.
¹² Hiroshima Astrophysical Science Center, Hiroshima University, Hiroshima, Japan.
¹³ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria, Australia.
¹⁴ Nucleo de Astronomia, Facultad de Ingenieria y Ciencias, Universidad Diego Portales, Santiago, Chile.
¹⁵ Centre for Radio Astronomy Research, University of Western Australia, Crawley, Western Australia, Australia.
¹⁶ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Canberra, Australian Capital Territory, Australia.
¹⁷ Kapteyn Astronomical Institute, University of Groningen, Groningen, the Netherlands.
¹⁸ Scuola Normale Superiore, Pisa, Italy.
¹⁹ Dipartimento di Fisica, Sapienza, Universita di Roma, Roma, Italy.
²⁰ INAF/Osservatorio Astrofisico di Arcetri, Firenze, Italy.
²¹ INFN, Roma, Italy.
²² Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA, USA.
²³ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA, USA.
²⁴ Sterrenkundig Observatorium, Ghent University, Gent, Belgium.
²⁵ Dept. of Physics & Astronomy, University College London, London, UK.
²⁶ Cornell University, Ithaca, NY, USA.
²⁷ INAF/Osservatorio Astronomico di Roma, Roma, Italy.
²⁸ Sapienza School for Advanced Studies, Roma, Italy.

PMID: 34552254
DOI: 10.1038/s41586-021-03846-z

Abstract

Over the past decades, rest-frame ultraviolet (UV) observations have provided large samples of UV luminous galaxies at redshift (z) greater than 6 (refs. ^1-3), during the so-called epoch of reionization. While a few of these UV-identified galaxies revealed substantial dust reservoirs^4-7, very heavily dust-obscured sources at these early times have remained elusive. They are limited to a rare population of extreme starburst galaxies^8-12 and companions of rare quasars^13,14. These studies conclude that the contribution of dust-obscured galaxies to the cosmic star formation rate density at z > 6 is sub-dominant. Recent ALMA and Spitzer observations have identified a more abundant, less extreme population of obscured galaxies at z = 3-6 (refs. ^15,16). However, this population has not been confirmed in the reionization epoch so far. Here, we report the discovery of two dust-obscured star-forming galaxies at z = 6.6813 ± 0.0005 and z = 7.3521 ± 0.0005. These objects are not detected in existing rest-frame UV data and were discovered only through their far-infrared [C II] lines and dust continuum emission as companions to typical UV-luminous galaxies at the same redshift. The two galaxies exhibit lower infrared luminosities and star-formation rates than extreme starbursts, in line with typical star-forming galaxies at z ≈ 7. This population of heavily dust-obscured galaxies appears to contribute 10-25% to the z > 6 cosmic star formation rate density.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't

Grants and funding

ERC_/European Research Council/International