Spectra of the CO or [CII] emission lines for the WISSH QSOs analysed in this work. For each source, the targeted transition is indicated by the top label. Spectra were extracted from the region where emission from the QSO host-galaxy is detected with S/N >  2 (see Fig. 3) and show the velocity range v ∈ [ − 2000, +2000] km s⁻¹ in channels of 40 km s⁻¹. In case of (e), we preferred a circular extraction region with size of the ALMA beam, centred on the QSO position, to limit contamination from a nearby line emitting source at 0.6 arcsec separation (see Fig. 3e). The best-fit, Gaussian profiles are shown by the red curve. The filled histogram indicates velocity channels in which emission in the QSO and companion spectra is > 5% than the peak flux of the best-fit model. Panels a and b: grey spectral regions were excluded from the fit because associated with line emission from nearby sources (see Sect. 3.2) partially unresolved by the NOEMA beam.