3 Data reduction

As in Papers I to IV, standard pre-processing was applied to the raw data, up to the rebinning in wavelength. The galaxy centers (r=0) were determined by a Gaussian fitting to a limited range ( $\simeq 12''$) around the intensity peak. In the outer regions, cosmic-ray hits were removed with a median filter, and adjacent lines were combined with a variable weighting function (a Gaussian continuously wider faintward). A Fourier-Fitting technique determined the central velocity dispersion $\sigma_0$ and, when possible, the radial profile $\sigma(r)$ of the dispersion, together with the projected rotation curve V(r) along the major axis. A two-pass mode (described in Paper I) allowed to remove cosmics on the inner lines, where the spatial resolution must be preserved. We adopted as $\sigma_0$ the dispersion measured on the line at r=0, or an interpolation between the values on the two lines bracketting the position r=0; similarly, the systemic velocity corresponds to r=0. Whenever possible, we have determined the maximum rotation velocity $V_{\rm max}$, as the mean of representative values along opposite semi-axes.