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Title: High-resolution CO and radio imaging of z similar to 2 ULIRGs: extended CO structures and implications for the universal star formation law
Authors: Bothwell, M. S.
Chapman, S. C.
Tacconi, L.
Smail, I.
Ivison, R. J.
Casey, C. M.
Bertoldi, F.
Beswick, R.
Biggs, A.
Blain, A. W.
Cox, P.
Genzel, R.
Greve, T. R.
Kennicutt, R.
Muxlow, T.
Neri, R.
Omont, A.
First Published: 11-Jun-2010
Publisher: Royal Astronomical Society (RAS)
Citation: Monthly Notices of the Royal Astronomical Society, 2010, 405 (1), pp. 219-233
Abstract: We present high spatial resolution (0.4 arcsec, Graphic kpc) Plateau de Bure Interferometer interferometric data on three ultraluminous infrared galaxies (ULIRGs) at Graphic: two submillimetre galaxies (SMGs) and one submillimetre faint star-forming radio galaxy. The three galaxies have been robustly detected in CO rotational transitions, either 12CO (J= 4Graphic3) or 12CO (J= 3Graphic2), allowing their sizes and gas masses to be accurately constrained. These are the highest spatial resolution observations observed to date (by a factor of Graphic2) for intermediate-excitation CO emission in Graphic ULIRGs. The galaxies appear extended over several resolution elements, having a mean radius of 3.7 kpc. High-resolution (0.3 arcsec) combined Multi-Element Radio-Linked Interferometer Network-Very Large Array observations of their radio continua allow an analysis of the star formation behaviour of these galaxies, on comparable spatial scales to those of the CO observations. This ‘matched beam’ approach sheds light on the spatial distribution of both molecular gas and star formation, and we can therefore calculate accurate star formation rates and gas surface densities: this allows us to place the three systems in the context of a Kennicutt–Schmidt (KS)-style star formation law. We find a difference in size between the CO and radio emission regions, and as such we suggest that using the spatial extent of the CO emission region to estimate the surface density of star formation may lead to error. This size difference also causes the star formation efficiencies within systems to vary by up to a factor of 5. We also find, with our new accurate sizes, that SMGs lie significantly above the KS relation, indicating that stars are formed more efficiently in these extreme systems than in other high-z star-forming galaxies.
DOI Link: 10.1111/j.1365-2966.2010.16480.x
ISSN: 0035-8711
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2010 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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