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arXiv · 1309.4459

The role of galaxy interaction in the SFR-M relation: characterizing morphological properties of Herschel-selected galaxies at 0.2<z<1.5

Chao-Ling Hung·David B. Sanders·Caitlin M. Casey·Nicholas Lee·Joshua E. Barnes·Peter Capak·Jeyhan S. Kartaltepe·Michael Koss·Kirsten L. Larson·Emeric Le Floc'h·Kelly Lockhart·Allison W. S. Man·Andrew W. Mann·Laurie Riguccini·Nicholas Scoville·Myrto Symeonidis
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Abstract

Galaxy interactions/mergers have been shown to dominate the population of IR luminous galaxies (log(LIR)>11.6Lsun) in the local Universe (z<0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M relation or the galaxy main sequence (MS)) have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy MS. Since the typical SFR at given M increases with redshift, the existence of galaxy MS implies that massive, IR-luminous galaxies at high-z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Herschel-PACS and -SPIRE observations covering the full 2-deg^2 COSMOS field provide one of the largest far-IR selected samples of high-redshift galaxies with well-determined redshifts to date, with sufficient sensitivity at z ~ 1, to sample objects lying on and above the galaxy MS. Using a detailed visual classification scheme, we show that the fraction of "disk galaxies" decreases and the fraction of "irregular" galaxies increases systematically with increasing LIR out to z ~ 1.5 and z ~ 1.0, respectively. At log(LIR) > 11.5 Lsun, >50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M relation, supporting the view that galaxies fall above the MS are more dominated by mergers than the MS galaxies. Meanwhile, we find that ~18% of massive IR-luminous MS galaxies are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.

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Chao-Ling Hung, David B. Sanders, Caitlin M. Casey, Nicholas Lee, Joshua E. Barnes, Peter Capak, Jeyhan S. Kartaltepe, Michael Koss, Kirsten L. Larson, Emeric Le Floc'h, Kelly Lockhart, Allison W. S. Man, Andrew W. Mann, Laurie Riguccini, Nicholas Scoville, Myrto Symeonidis. 2013-09-17. The role of galaxy interaction in the SFR-M relation: characterizing morphological properties of Herschel-selected galaxies at 0.2<z<1.5. https://doi.org/10.1088/0004-637x%2F778%2F2%2F129

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