The AT-LESS CO(1–0) survey of submillimetre galaxies in the Extended Chandra Deep Field South: first results on cold molecular gas in galaxies at z ∼ 2

Huynh, Minh T.; Emonts, B.H.C.; Kimball, A.E.; Seymour, N.; Smail, Ian; Swinbank, A.M.; Brandt, W.N.; Casey, C.M.; Chapman, S.C.; Dannerbauer, H.; Hodge, J.A.; Ivison, R.J.; Schinnerer, E.; Thomson, A.P.; van der Werf, P.; Wardlow, J.L.

doi:10.1093/mnras/stx156

The AT-LESS CO(1–0) survey of submillimetre galaxies in the Extended Chandra Deep Field South: first results on cold molecular gas in galaxies at z ∼ 2

Huynh, Minh T.; Emonts, B.H.C.; Kimball, A.E.; Seymour, N.; Smail, Ian; Swinbank, A.M.; Brandt, W.N.; Casey, C.M.; Chapman, S.C.; Dannerbauer, H.; Hodge, J.A.; Ivison, R.J.; Schinnerer, E.; Thomson, A.P.; van der Werf, P.; Wardlow, J.L.

Authors

Minh T. Huynh

B.H.C. Emonts

A.E. Kimball

N. Seymour

Professor Ian Smail ian.smail@durham.ac.uk
Emeritus Professor

Professor Mark Swinbank a.m.swinbank@durham.ac.uk
Professor

W.N. Brandt

C.M. Casey

S.C. Chapman

H. Dannerbauer

J.A. Hodge

R.J. Ivison

E. Schinnerer

A.P. Thomson

P. van der Werf

J.L. Wardlow

Abstract

We present the first results from our ongoing Australia Telescope Compact Array survey of 12CO(1–0) in Atacama Large Millimeter Array (ALMA)-identified submillimetre galaxies (SMGs) in the Extended Chandra Deep Field South. Strong detections of 12CO(1–0) emission from two SMGs, ALESS 122.1 (z = 2.0232) and ALESS 67.1 (z = 2.1230), were obtained. We estimate gas masses of Mgas ∼ 1.3 × 1011 M⊙ and Mgas ∼ 1.0 × 1011 M⊙ for ALESS 122.1 and ALESS 67.1, respectively, adopting αCO = 1.0. Dynamical mass estimates from the kinematics of the 12CO(1–0) line yields Mdyn sin2 i = (2.1 ± 1.1) × 1011 M⊙ and (3.2 ± 0.9) × 1011 M⊙ for ALESS 122.1 and ALESS 67.1, respectively. This is consistent with the total baryonic mass estimates of these two systems. We examine star formation efficiency, using the LFIR versus L′CO(1−0) LCO(1−0)′ relation for samples of local ultraluminous infrared galaxies (ULIRGs) and Luminous Infrared Galaxies (LIRGs), and more distant star-forming galaxies, with 12CO(1–0) detections. We find some evidence of a shallower slope for ULIRGs and SMGs compared to less luminous systems, but a larger sample is required for definite conclusions. We determine gas-to-dust ratios of 170 ± 30 and 140 ± 30 for ALESS 122.1 and ALESS 67.1, respectively, showing that ALESS 122.1 has an unusually large gas reservoir. By combining the 38.1 GHz continuum detection of ALESS 122.1 with 1.4 and 5.5 GHz data, we estimate that the free–free contribution to radio emission at 38.1 GHz is 34 ± 17 μJy, yielding a star formation rate (1400 ± 700 M⊙ yr−1) consistent with that from the infrared luminosity.

Citation

Huynh, M. T., Emonts, B., Kimball, A., Seymour, N., Smail, I., Swinbank, A., …Wardlow, J. (2017). The AT-LESS CO(1–0) survey of submillimetre galaxies in the Extended Chandra Deep Field South: first results on cold molecular gas in galaxies at z ∼ 2. Monthly Notices of the Royal Astronomical Society, 467(1), 1222-1230. https://doi.org/10.1093/mnras/stx156

Journal Article Type	Article
Acceptance Date	Jan 17, 2017
Online Publication Date	Jan 22, 2017
Publication Date	May 11, 2017
Deposit Date	Mar 9, 2017
Publicly Available Date	Mar 9, 2017
Journal	Monthly Notices of the Royal Astronomical Society
Print ISSN	0035-8711
Electronic ISSN	1365-2966
Publisher	Royal Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	467
Issue	1
Pages	1222-1230
DOI	https://doi.org/10.1093/mnras/stx156

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This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.