Position–velocity diagrams of NOEMA observations centred on estimated kinematic centre of disc₁ (first row) or on the estimated kinematic centre of disc₂ (second row) and computed on a one-spatial-pixel-wide slice either along the major axes (first column) or the minor axes (second column) of discs. v_c(R)sin(i) curves are represented on diagrams with position taken along the major axis (first column). Horizontal solid lines show the fitted systemic velocities, v_sys, of the discs, and horizontal dashed lines show v_sys ± V_maxsin(i). Violet lines correspond to disc₁ and orange curves to disc₂. The horizontal grey lines in the bottom right corner of each panel show the projection of the elliptical Gaussian NOEMA synthesised beam on the x-axis of the panel.