Comparison of the FWHM of the [ N II ]  and [ S II ]  emission lines from Palomar (top left) and HST (top right) spectra. NGC 4486 falls outside the plotting range. In the bottom left panel, we used the differences between the velocity defined at 10% and 90% of the total flux instead. In bottom right panel, we compare the FWHM of the [ O I ]  and [ S II ]  lines. Symbols as in Fig. 2.