THE ROLE OF GALAXY INTERACTION IN THE SFR-M* RELATION: CHARACTERIZING MORPHOLOGICAL PROPERTIES OF Herschel-SELECTED GALAXIES AT 0.2 < z < 1.5

Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L-IR greater than or similar to 10(11.6) L-circle dot) in the local universe (z less than or similar to 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 a given M-* increases with redshift, the existence of the galaxy main sequence 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. 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 less than or similar to 1.5 and z less than or similar to 1.0, respectively. At L-IR > 10(11.5) L-circle dot, greater than or similar to 50% of the objects showevident 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 falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that similar to 18% of massive IR-luminous main-sequence galaxies are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.