APEX/SEPIA660 [CII] spectrum at a velocity resolution of 70 km s⁻¹. The solid magenta line shows the average transmission during the observations (assuming elevation = 60°, PWV = 0.4 mm, and ambient temperature = 0° Celsius). We marked the redshifts and widths of the HeII line (Silva et al. 2018) and the AGN component in the CO(1−0) line (Emonts et al. 2016). The magenta- and cyan-dashed lines show the double Gaussian fit (sum in blue), where the redshift of the higher velocity component has been fixed to that of CO(1−0). The black line is the velocity exclusion region used for the baseline subtraction.