Pressure-supported ionized gas in S0 galaxies

Rotation curves and velocity dispersion profiles are presented for both the stellar and gaseous components of a sample of S0 galaxies. In all galaxies the central velocity dispersion of the ionized gas exceeds 150 km/s. In some galaxies the gas dispersion remains as high as the stellar one over an extended radial range, showing that random motions are crucial for the dynamical support of the gas. Such a pressure support may explain why the observed gas rotation curves in galaxy bulges often fall short of the circular velocity predicted from the stellar kinematic models. It is suggested that, in addition to the acquisition of external material, some of the observed gas in S0 galaxies may have been shed from bulge stars.