Maps of the line peak velocity (color) obtained from simultaneous Gaussian fits to the CH₃CN and/or CHCN J_K = 18_K − 17_K lines (see Sect. 3.4.4 for details). The names of the lines above each panel show the transitions that have been analyzed. The thin contours are a map of the integrated emission of the corresponding lines. The contours are in 2σ steps, starting from the 3σ level. The thick contours correspond to the 5σ level of the 890 μm continuum emission shown in Fig. 2b). The two stars mark the peak positions of SMA1 and SMA2 (Sect. 3.1.2).