Ionized gas in E/S0 galaxies with dust lanes
  We report the results of multicolour observations of 30 E/S0 galaxies with
dust lanes. For each galaxy we obtained broad-band images and narrow-band
images using interference filters isolating the H\alpha +[NII] emission lines
to derive the amount and morphology of dust and ionized gas. To improve the
wavelength coverage we retrieved data from the SDSS and 2MASS and combined
these with our data. Ionized gas is detected in 25 galaxies and shows in most
cases a smooth morphology, although knots and filamentary structure are also
observed in some objects. The extended gas distribution closely follows the
dust structure, with a clear correlation between the mass of both components.
An extinction law by the extragalactic dust in the dark lanes is derived and is
used to estimate the dust content of the galaxies. The derived extinction law
is used to correct the measured colours for intrinsic dust extinction and the
data are fitted with a stellar population synthesis model. We find that the
H-alpha emission and colours of most objects are consistent with the presence
of an "old" stellar population (~10 Gyr) and a small fraction of a "young"
population (~10-100 Myr). To check this we closely examine NGC5363, for which
archival Spitzer/IRAC and GALEX data are available, as a representative
dust-lane E/S0 galaxy of the sample.
