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The classification of galaxy mergers and isolated disks is key forunderstanding the relative importance of galaxy interactions and secularevolution during the assembly of galaxies. The kinematic properties of galaxiesas traced by emission lines have been used to suggest the existence of asignificant population of high-z star-forming galaxies consistent with isolatedrotating disks. However, recent studies have cautioned that post-coalescencemergers may also display disk-like kinematics. To further investigate therobustness of merger/disk classifications based on kinematic properties, wecarry out a systematic classification of 24 local (U)LIRGs spanning a range ofgalaxy morphologies: from isolated spiral galaxies, ongoing interactingsystems, to fully merged remnants. We artificially redshift the WiFeSobservations of these local (U)LIRGs to z=1.5 to make a realistic comparisonwith observations at high-z, and also to ensure that all galaxies have the samespatial sampling of ~900 pc. Using both kinemetry-based and visualclassifications, we find that the reliability of kinematic classification showsa strong trend with the interaction stage of galaxies. Mergers with two nucleiand tidal tails have the most distinct kinematic properties compared toisolated disks, whereas a significant population of the interacting disks andmerger remnants are indistinguishable from isolated disks. The high fraction oflate-stage mergers showing disk-like kinematics reflects the complexity of thedynamics during galaxy interactions. However, the exact fractions ofmisidentified disks and mergers depend on the definition of kinematicasymmetries and the classification threshold when using kinemetry-basedclassifications. Our results suggest that additional indicators such asmorphologies traced by stars or molecular gas are required to further constrainthe merger/disk classifications at high-z.

Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z