An ALMA survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS field: High-resolution dust continuum morphologies and the link between sub-millimetre galaxies and spheroid formation

Gullberg, B.; Smail, Ian; Swinbank, A.M.; Dudzevičiūtė, U.; Stach, S.M.; Thomson, A.P.; Almaini, O.; Chen, C.C.; Conselice, C.; Cooke, E.A.; Farrah, D.; Ivison, R.J.; Maltby, D.; Michałowski, M.J.; Simpson, J.M.; Scott, D.; Wardlow, J.L.; Weiss, A.

doi:10.1093/mnras/stz2835

An ALMA survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS field: High-resolution dust continuum morphologies and the link between sub-millimetre galaxies and spheroid formation

Gullberg, B.; Smail, Ian; Swinbank, A.M.; Dudzevičiūtė, U.; Stach, S.M.; Thomson, A.P.; Almaini, O.; Chen, C.C.; Conselice, C.; Cooke, E.A.; Farrah, D.; Ivison, R.J.; Maltby, D.; Michałowski, M.J.; Simpson, J.M.; Scott, D.; Wardlow, J.L.; Weiss, A.

Authors

B. Gullberg

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

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

Ugne Dudzeviciute ugne.dudzeviciute2@durham.ac.uk
PGR Student Doctor of Philosophy

S.M. Stach

A.P. Thomson

O. Almaini

C.C. Chen

C. Conselice

E.A. Cooke

D. Farrah

R.J. Ivison

D. Maltby

M.J. Michałowski

J.M. Simpson

D. Scott

J.L. Wardlow

A. Weiss

Abstract

We present an analysis of the morphology and profiles of the dust continuum emission in 153 bright sub-millimetre galaxies (SMGs) detected with ALMA at signal to noise ratios of >8 in high-resolution 0′′.18 (∼1 kpc) 870 μm maps. We measure sizes, shapes and light profiles for the rest-frame far-infrared emission from these luminous star-forming systems and derive a median effective radius (Re) of 0′′.10 ± 0′′.04 for our sample with a median flux of S870=5.6 ± 0.2 mJy. We find that the apparent axial ratio (b/a) distribution of the SMGs peaks at b/a ∼ 0.63 ± 0.02 and is best described by triaxial morphologies, while their emission profiles are best fit by a Sérsic model with n ≃ 1.0 ± 0.1, similar to exponential discs. This combination of triaxiality and n ∼ 1 Sérsic index are characteristic of bars and we suggest that the bulk of the 870 μm dust continuum emission in the central ∼2 kpc of these galaxies arises from bar-like structures. As such we caution against using the orientation of shape of the bright dust continuum emission at ≂ resolution to assess either the orientation of any disc on the sky or tits inclination. By stacking our 870 μm maps we recover faint extended dust continuum emission on ∼4 kpc scales which contributes 13 ± 1% of the total 870 μm emission. The scale of this extended emission is similar to that seen for the molecular gas and rest-frame optical light in these systems, suggesting that it represents an extended dust and gas disc at radii larger than the more active bar component. Including this component in our estimated size of the sources we derive a typical effective radius of ≃ 0′′.15 ± 0′′.05 or 1.2 ± 0.4 kpc. Our results suggest that kpc-scale bars are ubiquitous features of high star-formation rate systems at z ≫ 1, while these systems also contain fainter and more extended gas and stellar envelopes. We suggest that these features, seen some 10–12 Gyrs ago, represent the formation phase of the earliest galactic-scale components: stellar bulges.

Citation

Gullberg, B., Smail, I., Swinbank, A., Dudzevičiūtė, U., Stach, S., Thomson, A., …Weiss, A. (2019). An ALMA survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS field: High-resolution dust continuum morphologies and the link between sub-millimetre galaxies and spheroid formation. Monthly Notices of the Royal Astronomical Society, 490(4), 4956-4974. https://doi.org/10.1093/mnras/stz2835

Journal Article Type	Article
Acceptance Date	Sep 30, 2019
Online Publication Date	Oct 14, 2019
Publication Date	Dec 31, 2019
Deposit Date	Oct 17, 2019
Publicly Available Date	Oct 17, 2019
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	490
Issue	4
Pages	4956-4974
DOI	https://doi.org/10.1093/mnras/stz2835

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Copyright Statement
This article has been accepted for publication in the Monthly notices of the Royal Astronomical Society ©: 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.