Counter-rotation in dust-lane ellipticals and the implications for accretion events in galaxies

Here we present new observations on four major-axis dust-lane ellipticals, Anon 1029-459, NGC3528, NGC4370 and NGC5745. In the first two of these we observe counter-rotation of gas and stars, whereas the two components are co-rotating in NGC4370 and NGC5745; these results are consistent with the acquisition hypothesis. The same accretion events occur also in SO galaxies, where they give rise to polar rings or to counter-and co-rotating gas in the equatorial plane. As dynamic decoupling in these latter galaxies appears common, we suggest that in all SOs with extended emission lines the gas is of external origin. (author)