In the local universe, Ultraluminous Infrared Galaxies (ULIRGs, L_IR>10^12 L_sun) are all interacting and merging galaxies. To date, studies of ULIRGs at high redshift have found a variety of results due to their varying selection effects and small sample sizes. Some studies have found that mergers still dominate the galaxy morphology while others have found a high fraction of morphologically normal or clumpy star forming disks. Near-infrared imaging is crucial for interpreting galaxy structure at high redshift since it probes the rest frame optical light of a galaxy and thus we can compare directly to studies in the local universe. Here, we present the results of a morphological analysis of a sample of high redshift (z~1-3) ULIRGs and compare these results to those at lower redshift in order to constrain how the role of mergers has evolved over cosmic time. These galaxies are selected based on their infrared luminosities measured using 100 and 160 micron data from the GOODS-Herschel coverage of GOODS-S. We visually classified all of the ULIRGs as well as a comparison sample with the same redshift and H band magnitude range using ACS and WFC3 data from the GOODS and CANDELS surveys. In addition, we present the results of a near-infrared spectroscopic campaign for a large number of high redshift (z>1) ULIRGs in the COSMOS and GOODS fields, with well constrained luminosities from Spitzer and Herschel measurements. We use standard optical diagnostics to study the relative contribution of star formation and AGN activity in this sample and compare our results using several other commonly used diagnostics at these redshifts. We then combine this information with the morphologies to investigate the interconnected role that galaxy mergers and AGN may play among these systems.

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