AN H-ALPHA SURVEY OF CLUSTER SPIRALS - COMPARISON OF STAR FORMATION IN CLUSTERS AND THE FIELD

In an objective prism survey of eight nearby Abell clusters, we have detected Halpha emission from 77 out of a total of 201 CGCG spiral galaxies. We find that detection of Halpha emission is approximately independent of galaxy absolute magnitude, distance to the cluster center, and the presence of a bar. However, tidally distorted spirals are much more likely to be detected than undistorted spirals. Furthermore, there is a strong tendency for tidally distorted spirals to have compact nuclear emission rather than more extended disk-wide emission. When compared to field spirals, we find that late-type (Sc and Sc-Irr) cluster spirals have less Halpha emission, while early-type (Sa and Sab) cluster spirals can have significantly enhanced emission. The enhanced emission is most likely to be due to tidally induced star formation from galaxy-galaxy interactions.