Example of the emission line properties. Left: [O III] emission line image of 3C 33. The white dotted lines mark the radio position angle, the solid white lines show the orientation of the emission line structures on both sides of the nucleus, and the gray line marks the orientation of the kinematical axis in the inner regions measured with kinemetry (see Sect. 2.2). The rectangle represents the region from which we extracted the velocity curve shown in the right panel. Data were extracted on each pixel in the innermost regions and then at distances of 1″. The length of the gray bars represents the line width at each location.