Spatial distribution of CH₃NCO (top left panel) together with those of several molecular species as identified at the top of each panel. The data are from ALMA Science Verification observations. The different positions discussed in the text are indicated by symbols (white triangle: source I; white circle: source n; ×: the compact ridge; cyan unfilled square/triangle: Positions A/B, which are the two emission peaks of CH₃NCO). Additional molecular emission maps are shown in Fig. B.3.