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CO and JHK Observations of E and S0 Galaxies


New multiaperture infrared photometric observations of the central regions of 51 early-type galaxies and of the integrated light of five globular clusters are presented. These data are compared with selected optical observations and with various model predictions. The main results of the work are: (1) the observed parameters for the brighter galaxies, particularly the CO index and the V - K color, agree with the predictions of stellar synthesis models characterized by giant-dominated populations with M / LV < 10; (2) the galaxian broad-band colors tend to redden with increasing luminosity and decreasing aperture size; (3) for the globular clusters, there is evidence that the integrated colors become redder with increasing metallicity; (4) in bright galaxies the relative changes of U - V, V - J, and J - K as functions of radius differ from the relative changes as functions of luminosity at a fixed radius.

Subject headings: galaxies: photometry - galaxies: stellar content - globular clusters: photometry - stars: late-type - infrared: general