Schematic representation of the morphological and symmetrical features in the major axis PV diagrams considered for the computation of the P parameters defined in Sect. 7.1. Left panel: PV diagram for a representative thin rotating disk model along the major axis. The dotted gray horizontal line shows the position of the systemic velocity that divides the major-axis PV diagram into regions A1 and A2, while the dotted gray vertical lines indicate the center dividing A1 and A2 into two regions, l and r. The ith representative pixels used for the computation of P_major are shown in the regions A1 and A2, respectively. The blue dotted contours enclose the 20% brightest pixels, and the yellow crosses are their flux-weighted centroids. The black plus indicates the outermost radius used for the extraction of the kinematic parameters, and the solid orange lines are V_los, out, the average values of the galaxy line-of-sight velocities. The double arrow indicates ΔV, the extension along the velocity axis for one of the peak distributions. The major-axis PV diagrams from the high S/N, low-resolution mock data of the disk Lantana and merger Adenia are shown in the central and right panels.