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Tracing cool molecular gas and star formation on ∼100 pc scales within a z ∼ 2.3 galaxy

Thomson, A.P.; Ivison, R.J.; Owen, Frazer N.; Danielson, A.L.R.; Swinbank, A.M.; Smail, Ian

Tracing cool molecular gas and star formation on ∼100 pc scales within a z ∼ 2.3 galaxy Thumbnail


A.P. Thomson

R.J. Ivison

Frazer N. Owen

A.L.R. Danielson


We present new, high-angular resolution interferometric observations with the Karl G. Jansky Very Large Array of 12CO J = 1−0 line emission and 4–8 GHz continuum emission in the strongly lensed, z = 2.3 submillimetre galaxy, SMM J21352-0102. Using these data, we identify and probe the conditions in ∼100 pc clumps within this galaxy, which we consider to be potential giant molecular cloud complexes, containing up to half of the total molecular gas in this system. In combination with far-infrared and submillimetre data, we investigate the far-infrared/radio correlation, measuring qIR = 2.39 ± 0.17 across SMM J21352. We search for variations in the properties of the interstellar medium (ISM) throughout the galaxy by measuring the spatially resolved qIR and radio spectral index, αradio, finding ranges qIR =[2.1, 2.6] and αradio = [−1.5, −0.7]. We argue that these ranges in αradio and qIR may reflect variations in the age of the ISM material. Using multi-J 12CO data, we quantitatively test a recent theoretical model relating the star formation rate surface density to the excitation of 12CO, finding good agreement between the model and the data. Lastly, we study the Schmidt–Kennicutt relation, both integrated across the system and within the individual clumps. We find small offsets between SMM J21352 and its clumps relative to other star-forming galaxy populations on the Schmidt–Kennicutt plot – such offsets have previously been interpreted as evidence for a bi-modal star formation law, but we argue that they can be equally well explained as arising due to a combination of observational uncertainties and systematic biases in the choice of model used to interpret the data.

Journal Article Type Article
Acceptance Date Jan 6, 2015
Publication Date Apr 1, 2015
Deposit Date Apr 13, 2015
Publicly Available Date Oct 22, 2015
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 448
Issue 2
Pages 1874-1886
Keywords ISM: molecules, Galaxies: active, Galaxies: high-redshift, Galaxies: ISM, Galaxies: starburst.
Public URL


Published Journal Article (777 Kb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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