Position of the shells B1a, B1b, and B2 in the outflow, according to the tomographic analysis in Section 4.1. The coordinates of the SE and NW apexes of the ellipse fit as in Table 1 are superposed to an intensity (moment 0) map of the redshifted lobe integrated over the velocity range 10.6–16.2 km s⁻¹ (characteristic of the considered traces), rotated clockwise by 48°to have the system axis along the vertical direction. The magenta ellipses are contours of the continuum emission at 10 and 200σ_c. The ellipse in the upper right corner is the beam size in CO maps.