Panel a: same colour scale as in Fig. 2c, showing the thermal dust emission without the larger scale core emission in order to enhance the structure of the inner envelope. The colour lines show the 50% contour of the peak emission of v_t = 1 CH₃ OH line at different velocities, starting from − 50.5 km s⁻¹ (blue) to − 38 km s⁻¹ (red). The corresponding velocity of every second contour is shown in the figure legend. Panel b: same as the left panel, but showing the90% contours of the most extreme velocity components in red and blue. The velocities corresponding to each contour are shown in the figure legend.