Spectra of four molecular lines in T_sb scale towards the peak of the 890 μm continuum emission, i.e., SMA1. The SiO and H¹³CO⁺ intensities are scaled by a factor 2.0. The vertical dashed line indicates the systemic velocity (V_sys) of the cloud, V_LSR  =  41.6 km s^-1. In the CO isotopomers spectra, we mark the positions of all possible (molecular) lines, calculated assuming that they are emitted with velocity equal to V_sys (see Sect. 3.3.2). The thick horizontal blue and red bars denote the velocity intervals over which the line emission has been integrated to produce the maps in Figs. 9, 10, and 16. The emission seen around V_LSR  ≃  70 km s^-1 of the C¹⁸O spectrum probably originates in the HNCO line rather than CHCN 18₁₆ − 17₁₆.