Panel a: position-velocity diagram, extracted from a 0.3 arcsec slit centred on the QSO location along the major kinematic axis (see Fig. 4a) corresponding to a PA of 165 deg (measured anti-clockwise from north). Black contours refer to the [2, 3, 4, …2ⁿ]σ significance level of the CO(3−2) emission, with σ = 0.083 mJy beam⁻¹ and n >  2. The contours associated with the best-fit ^3DBAROLO model of the kinematics are also shown by the blue contours. Panels b and c: zoom-in of the velocity range v ∈ [ − 500, +600] km s⁻¹ with increased angular resolution (0.16 × 0.19 arcsec²), extracted along and perpendicular to the major kinematic axis, respectively. Contours are as in the top panel, with σ = 0.16 mJy beam⁻¹.