The Morphological Types and Orbits of H i Deficient Spirals in Clusters of Galaxies

Further analysis of the Giovanelli and Haynes catalog of the H I content of cluster spirals reveals that H I deficiency is strongly correlated with morphological type. Those spirals deficient in H I are predominantly early-type galaxies; spirals of type Sbc and later are rarely found to be gas deficient, even though they often reside in the same dense environments. Comparison of the velocity dispersion as a function of radius for gas-poor and gas-rich spirals indicates that the gas-poor spirals are on radial orbits which carry them into the dense environment of the cluster core, while the orbits of gas-rich spirals are more likely to be isotropic or even circular. The simplest interpretation of these data is that ram pressure stripping of spiral galaxies on radial orbits is responsible for H I deficiency.