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.