Left panel: blueshifted CO component is integrated between peak_blue−2σ_blue = −1340 km s^-1 and CO_sys−3σ_sys = −700 km s^-1 (i.e. according to the Gaussian fit in Table 2). Levels start at ± 2σ and increase (decrease) by 0.5σ (σ = 39μJy/beam for an integrated bandwidth of 240 MHz = 767 km s^-1). Middle panel: the CO systemic line integrated in the range Line−peak ± 3σ is shown. Levels start at ± 2σ and increase (decrease) by 5σ (σ = 27.7μJy/beam for 480 MHz (=1533 km s^-1) integrated bandwidth). Right panel: the line at 93.85 GHz integrated in the range Line−peak ± 3σ is shown. Levels start at ± 2σ and increase (decrease) by 1σ (σ = 34μJy/beam per 320 MHz =1022 km s^-1 integrated bandwidth). The cross denotes the phase tracking centre and is 4 × 4 arcsec wide.