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Session 80 - Stellar Population in Cluster Galaxies.
Display session, Wednesday, January 15
Metropolitan Ballroom,
Does the environment influence recent star formation in clusters? Analyses of H\alpha and R images of 65 Virgo cluster galaxies and a control sample of 35 isolated galaxies show that massive star formation in the Virgo cluster has been influenced by a variety of environmental effects.
The outer star-forming disks of many Virgo cluster galaxies are truncated, consistent with gas stripping by the environment. The inner disks span a larger range in H\alpha surface brightness than comparable isolated galaxies, consistent with disk fading in some cases and star formation enhancements in others. Truncation of the star-forming disks is most severe for earlier type spirals and for a population of 'peculiar early-type' spirals. Peculiar early-type spirals are small bulge, gas-deficient galaxies with featureless outer disks, but strong circumnuclear star formation. Although the Hubble classification seems to adequately describe the morphology of many Virgo cluster galaxies, it may break down for the peculiar early-type spirals. Some of these galaxies have inner H\alpha profiles similar to the average Sc profile derived from Virgo cluster and isolated Sc's, suggesting that they may be severely stripped Sc galaxies. Others, however, have circumnuclear H\alpha emission which is enhanced with respect to both Virgo cluster and isolated Sa's and Sc's. At least one of these galaxies is a recent merger product. We present images, radial profiles, and an asymmetry analysis of the sample galaxies.
