Example of the [O III] emission-line profile (blue curve) of 3C 033 in the brightest spaxel of the image. The vertical orange line represents the velocity of the peak flux density (v_p), and the green vertical lines show the 10th (v₁₀) and 90th (v₉₀) velocity percentiles, which are used for the definition of the velocity width of the line that contains 80% of the emission line flux (W₈₀). In this spectrum the redshifted wing dominates, producing a positive value of the asymmetry (R > 0). The dotted red horizontal line is the continuum, linearly interpolated and subtracted.