The ratio of bulk to turbulent velocity (parametrized as Δv/ 2σ, see Sect. 7.5) in the 25 sources with extended gas in Table 4 scales with the size of the emission-line region (top panel). We plot Δv/ 2 instead of Δv, because this gives an approximation to the circular velocity in case of rotationally dominated motion. The offset between maximal and average FWHM does however not depend on the source size (bottom panel).