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Several very luminous galaxies were examined to determine the contribution of active nuclei to their luminosity and the nature of their stellar population. A suite of galaxy properties including bolometric luminosity, near-infrared luminosity, ionizing continuum luminosity, and CO index were observed. Masses of the central regions were obtained for seven galaxies, using the 2.3 $\mu$m bands of CO. Models of young stellar populations were compared to the observed properties of the galaxies.
It was found that up to half of the galaxies have properties which are inconsistent with those of stellar populations. The active nuclei of these galaxies generally produce more than half the total light of the galaxies, but less than one-third of the 2.2 $\mu$m light. The galaxies containing AGN also have young stellar populations. There is no evidence for the existence of active nuclei in other galaxies.
The stellar populations that dominate the starlight in the galaxies have a wide range of properties. Stellar populations range in age from 10 to 65 Myr. The timescale for star formation ranges from 5 Myr to 100 Myr. The local initial mass function is ruled out for one galaxy: the stellar population in NGC 1614 must have a higher ratio of high-mass to low-mass stars than that seen in local star forming regions.
