COLORS, LUMINOSITIES, AND MASSES OF DISK GALAXIES .2. ENVIRONMENTAL DEPENDENCIES

The B-band and near-infrared (H) luminosity functions of spiral galaxi es are derived for the Coma and A1367 clusters and for a reference pop ulation of ''field'' galaxies in the Coma supercluster. They are consi stent at the bright end, but they differ significantly at the faint en d, indicating an overdensity of spirals with blue color (B-H < 3.0) an d faint H luminosity (H > -21.5) in clusters with respect to the field . These objects have disturbed morphology and peculiar velocities sign ificantly larger than the rest of the cluster sample. We discuss these results in the framework of a possible environmental dependence of ga laxy evolution, and we conclude that enhanced current star formation i n cluster spiral galaxies might occur due to molecular gas collapse st imulated by the ram-pressure mechanism.