Spectra of the CH₃CN (19_K–18_K) transitions along the eastern (left column) and western (right column) sides of the disk plane. Spectra are integrated at radial steps of 500 au as indicated in Fig. 1, and each pointing is labelled on the top left accordingly. The CH₃CN components, with K ranging from 0 to 10, are marked in red in each spectrum. The brightest line at a rest frequency of 349.107 GHz corresponds to the CH₃OH (14_1,13–14_1,14) A⁺ emission imaged in Fig. 2. Modelled spectra are overplotted in red; we note that the first four K components were not fitted, except at positions P6 and P12 (cf. Sect. 3).