Preprint typeset using LATEX style emulateapj v. 04/17/13 THE ROLE OF GALAXY INTERACTION IN THE SFR-M ∗ RELATION: CHARACTERIZING MORPHOLOGICAL PROPERTIES OF HERSCHEL-SELECTED GALAXIES AT 0.2 < Z < 1.5

Abstract

Galaxy interactions/mergers have been shown to dominate the population of infrared luminous galaxies (LIR & 1011.6L) 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”) have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at givenM ∗ increases with redshift, the existence of galaxy main sequence implies that massive, infrared 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-deg2 COSMOS field provide one of the largest far-infrared 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 main sequence. 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 LIR> 1011.5 L, & 50 % of the objects show eviden