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Probing star formation relations of mergers and normal galaxies across the CO ladder

Published online by Cambridge University Press:  12 September 2016

Thomas R. Greve*
Affiliation:
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom email: t.greve@ucl.ac.uk
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Abstract

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We examine integrated luminosity relations between the IR continuum and the CO rotational ladder observed for local (ultra) luminous infra-red galaxies ((U)LIRGs, LIR ≥ 1011 M) and normal star forming galaxies in the context of radiation pressure regulated star formation proposed by Andrews & Thompson (2011). This can account for the normalization and linear slopes of the luminosity relations (log LIR = α log L'CO + β) of both low- and high-J CO lines observed for normal galaxies. Super-linear slopes occur for galaxy samples with significantly different dense gas fractions. Local (U)LIRGs are observed to have sub-linear high-J (Jup > 6) slopes or, equivalently, increasing LCOhigh-J/LIR with LIR. In the extreme ISM conditions of local (U)LIRGs, the high-J CO lines no longer trace individual hot spots of star formation (which gave rise to the linear slopes for normal galaxies) but a more widespread warm and dense gas phase mechanically heated by powerful supernovae-driven turbulence and shocks.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2016 

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