Journal Article

A CO(3–2) survey of a merging sequence of luminous infrared galaxies

J. Leech, K. G. Isaak, P. P. Papadopoulos, Y. Gao and G. R. Davis

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 2, pages 1364-1378
Published in print August 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16775.x
A CO(3–2) survey of a merging sequence of luminous infrared galaxies

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Luminous infrared galaxies (LIR > 1011 L) are often associated with interacting galactic systems and are thought to be powered by merger-induced starbursts and/or dust-enshrouded active galactic nucleus. In such systems, the evolution of the dense, star-forming molecular gas as a function of merger separation is of particular interest. Here, we present observations of the CO(3–2) emission from a sample of luminous infrared galaxy mergers that span a range of galaxy–galaxy separations. The excitation of the molecular gas is studied by examining the CO(3–2)/CO(1–0) line ratio, r31, as a function of merger extent. We find these line ratios, r31, to be consistent with kinetic temperatures of Tk= (30–50) K and gas densities of . We also find weak correlations between r31 and both merger progression and star formation efficiency [LFIR/LCO(1-0)]. These correlations show a tendency for gas excitation to increase as the merger progresses and the star formation efficiency rises. To conclude, we calculate the contributions of the CO(3–2) line to the 850-μm fluxes measured with SCUBA (Submillimetre Common-User Bolometer Array), which are seen to be significant (∼22 per cent).

Keywords: ISM: molecules; galaxies: interactions; galaxies: ISM; galaxies: starburst; infrared: galaxies

Journal Article.  6840 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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