PRESSURE-SUPPORTED IONIZED-GAS IN SO GALAXIES

Rotation curves and velocity dispersion profiles are presented for bot h the stellar and gaseous components of a sample of S0 galaxies. In al l galaxies the central velocity dispersion of the ionized gas exceeds 150 km s(-1). In some galaxies the gas dispersion remains as high as t he stellar one over an extended radial range, showing that random moti ons are crucial for the dynamical support of the gas. Such a pressure support may explain why the observed gas rotation curves in galaxy bul ges often fall short of the circular velocity predicted from the stell ar kinematic models. It is suggested that, in addition to the acquisit ion of external material, some of the observed gas in SO galaxies may have been shed from bulge stars.