Left panel: strength of the third Gauss-Hermite coefficient h₃ representing an asymmetry in the line profile found to be significant only in 4 galaxies, i.e. Mrk 1014, PG 1612 + 261, SDSS J1655 + 2146, and SDSS J0836 + 4426. The black contours represent the [O iii] surface brightness distribution for comparison and the blue cross marks the QSO position for reference. Right panel: modelling of [O iii] λ4960,5007 doublet line in the co-added spectra (of the spaxels in the magenta box on the left) with two Gaussian components. The red line is the model to the measured spectrum shown in black, and the green line represents the individual Gaussian components.