An ALMA survey of the S2CLS UDS field: optically invisible submillimetre galaxies
Artikel i vetenskaplig tidskrift, 2021

We analyse a robust sample of 30 near-infrared-faint (K-AB > 25.3, 5 sigma) submillimetre galaxies (SMGs) selected from a 0.96 deg(2) field to investigate their properties and the cause of their faintness in optical/near-infrared wavebands. Our analysis exploits precise identifications based on Atacama Large Millimeter Array (ALMA) 870-mu m continuum imaging, combined with very deep near-infrared imaging from the UKIDSS Ultra Deep Survey. We estimate that SMGs with K-AB > 25.3 mag represent 15 +/- 2 per cent of the total population brighter than S-870 = 3.6 mJy, with a potential surface density of similar to 450 deg(-2) above S870 >= 1 mJy. As such, they pose a source of contamination in surveys for both high-redshift 'quiescent' galaxies and very high redshift Lyman-break galaxies. We show that these K-faint SMGs represent the tail of the broader submillimetre population, with comparable dust and stellar masses to K-AB <= 25.3 mag SMGs, but lying at significantly higher redshifts (z = 3.44 +/- 0.06 versus z = 2.36 +/- 0.11) and having higher dust attenuation (A(V) = 5.2 +/- 0.3 versus A(V) = 2.9 +/- 0.1). We investigate the origin of the strong dust attenuation and find indications that these K-faint galaxies have smaller dust continuum sizes than the K-AB <= 25.3 mag galaxies, as measured by ALMA, which suggests their high attenuation is related to their compact sizes. We identify a correlation of dust attenuation with star formation rate surface density (Sigma(SFR)), with the K-faint SMGs representing the higher Sigma(SFR) and highest A(V) galaxies. The concentrated, intense star formation activity in these systems is likely to be associated with the formation of spheroids in compact galaxies at high redshifts, but as a result of their high obscuration these galaxies are completely missed in ultraviolet, optical, and even near-infrared surveys.

galaxies: formation

galaxies: evolution

cosmology: observations

submillimetre: galaxies


Ian Smail

Durham University

U. Dudzeviciute

Durham University

S. M. Stach

Durham University

O. Almaini

University of Nottingham

J. E. Birkin

Durham University

S. C. Chapman

Dalhousie University

Chian-Chou Chen

Academia Sinica

J. E. Geach

University of Hertfordshire

Bitten Gullberg

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

J. A. Hodge

Universiteit Leiden

S. Ikarashi

Durham University

R. J. Ivison

European Southern Observatory Santiago

D. Scott

University of British Columbia (UBC)

Chris Simpson

Gemini Observatory North

A. M. Swinbank

Durham University

A. P. Thomson

University of Manchester

F. Walter


J. L. Wardlow

Lancaster University

P. van der Werf

Universiteit Leiden

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 502 3 3426-3435


Meteorologi och atmosfärforskning

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik



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