Luminosity Profiles of Merger Remnants

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Abstract
Using published luminosity and molecular gas profiles of the late-stage mergers NGC 3921, NGC 7252, and Arp 220, we examine the expected luminosity profiles of the evolved merger remnants, especially in light of the massive CO complexes that are observed in their nuclei. For NGC 3921 and NGC 7252, we predict that the resulting luminosity profiles will be characterized by an r1/4 law. In view of previous optical work on these systems, it seems likely that they will evolve into normal elliptical galaxies as regards their optical properties. Due to a much higher central molecular gas column density, Arp 220 might not evolve such a "seamless" light profile. We conclude that ultraluminous infrared mergers such as Arp 220 either evolve into elliptical galaxies with anomalous luminosity profiles or do not produce many low-mass stars out of their molecular gas complexes.