Panel a: velocity-integrated map of the blue-shifted (v <  −250 km s⁻¹) CO(3−2) emission obtained by integrating the emission detected at > 3σ in each 30 km s⁻¹ spectral channel, for at least four contiguous channels (i.e. over a velocity range of ≥120 km s⁻¹). White contours show the systemic CO(3−2) emission (same as Fig. 1a). Panel b: CO(3−2) spectra of the extended outflowing clumps A and B shown in panel a, together with their best-fit multi-Gaussian components model. The spectrum extracted at the position of clump A (top panel), located at ∼1.8 kpc from the QSO, shows CO(3−2) emission centred at v ∼ 0 (systemic emission from the QSO, green curve) plus two components with blue-shifted velocities of v ∼ −300 and ∼ − 700 km s⁻¹. The spectrum extracted at the position of clump B (bottom panel) shows no contamination from the CO(3−2) systemic emission, while blue-shifted emission is detected at v ∼ −400 km s⁻¹.