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S.M. Bracht, C.C. Lambrecht, L.M. Young (New Mexico Tech)
Detailed studies of simulated galaxy-galaxy mergers and comparisons to disky elliptical galaxies suggest that dissipational cold gas must have been important in the formation of disky ellipticals. Conversely, if boxy elliptical galaxies formed in major mergers then they were probably gas-poor mergers.
These hypotheses make a testable prediction; if cold gas is necessary for the formation of disky systems but not for boxy systems, we might expect the CO detection rate to be higher among the disky ellipticals than the boxy ones. To test this prediction, we have obtained V and I imaging of 57 far-IR bright elliptical and E/S0 galaxies. The galaxies range in luminosity from MB = -16 to -22, with 60% brighter than MB = -20. We characterize their shapes by measuring deviations from perfect elliptical isophotes (a4) near the effective radius. From this we are able to compare the distribution of CO detections and nondetections among boxy and disky galaxies, giving us clues to the formation and evolution of early-type galaxies. Our sample contains roughly equal numbers of boxy, disky, and intermediate or mixed types, as one would expect based on the sample's magnitude range.
The CO detection rate is roughly the same (40%) in all three classes; this result suggests that the stellar disks observed in the disky types are not related to the present molecular gas disks.
The funding agency for this research is New Mexico Tech in Socorro, New Mexico.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.