THE DISTRIBUTION OF IONIZED-GAS IN EARLY-TYPE GALAXIES

We present and discuss Halpha+[N II] imaging observations of fifteen n earby elliptical and SO galaxies with extended optical emission lines. The morphology of the emitting regions suggests that the ionized gas usually lies in a disk which is often geometrically decoupled from the stellar body, as expected in a triaxial galaxy. The presence of a gas eous disk makes these galaxies suitable for testing their gravitationa l field in a straightforward way. The presence of dust in many of the disks, together with the observed morphological properties, suggests t hat the ionized gas in most of these galaxies is more closely associat ed with the cold ISM than with the hot X-ray component. The mass of io nized gas in the galaxies studied here is typically 10-100 times that in a 'normal' early-type galaxy of similar optical luminosity. These a ppear to be galaxies where an unusually high fraction of the cold gas has been ionized, rather than unusually gas-rich systems in an overall sense. The extra ionizing source may be related to an active nucleus, since the continuum radio emission from these galaxies is typically 1 0-15 times more powerful than in 'normal' ellipticals of the same opti cal luminosity.