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An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS Field (AS2COSPEC): Survey Description and First Results

Chen, Chian-Chou; Liao, Cheng-Lin; Smail, Ian; Swinbank, A.M.; Ao, Y.; Bunker, A.J.; Chapman, S.C.; Hatsukade, B.; Ivison, R.J.; Lee, Minju M.; Serjeant, Stephen; Umehata, Hideki; Wang, Wei-Hao; Zhao, Y.

An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS Field (AS2COSPEC): Survey Description and First Results Thumbnail


Chian-Chou Chen

Cheng-Lin Liao

Y. Ao

A.J. Bunker

S.C. Chapman

B. Hatsukade

R.J. Ivison

Minju M. Lee

Stephen Serjeant

Hideki Umehata

Wei-Hao Wang

Y. Zhao


We introduce an ALMA band 3 spectroscopic survey targeting the brightest submillimeter galaxies (SMGs) in the COSMOS field. Here we present the first results based on the 18 primary SMGs that have 870 μm flux densities of S870 = 12.4–19.3 mJy and are drawn from a parent sample of 260 ALMA-detected SMGs from the AS2COSMOS survey. We detect emission lines in 17 and determine their redshifts to be in the range of z = 2–5 with a median of 3.3 ± 0.3. We confirm that SMGs with brighter S870 are located at higher redshifts. The data additionally cover five fainter companion SMGs, and we obtain line detection in one. Together with previous studies, our results indicate that for SMGs that satisfy our selection, their brightest companion SMGs are physically associated with their corresponding primary SMGs ≥40% of the time, suggesting that mergers play a role in the triggering of star formation. By modeling the foreground gravitational fields, <10% of the primary SMGs can be strongly lensed with a magnification μ > 2. We determine that about 90% of the primary SMGs have lines that are better described by double Gaussian profiles, and the median separation of the two Gaussian peaks is 430 ± 40 km s−1. This allows estimates of an average baryon mass, which, together with the line dispersion measurements, puts our primary SMGs on the similar mass–σ correlation found on local early-type galaxies. Finally, the number density of our z > 4 primary SMGs is found to be ${1}_{-0.6}^{+0.9}\times {10}^{-6}$ cMpc−3, suggesting that they can be the progenitors of z ∼ 3−4 massive quiescent galaxies.

Journal Article Type Article
Acceptance Date Mar 27, 2022
Online Publication Date Apr 25, 2022
Publication Date Apr 20, 2022
Deposit Date Jun 8, 2022
Publicly Available Date Jun 8, 2022
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 929
Issue 2
Article Number 159
Public URL


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