CO(1−0) luminosity as a function of redshift for the PHz-IRAM sources. Symbols are the same as in Fig. 10. The purple and magenta curves show the expected rms at, respectively, 3 mm (E090), and 2 mm (E150) reached in 5 h of integration time in the summer (dashed curve) and in the winter (dotted curve) semesters, assuming average conditions, and a resolution of 45 km s⁻¹. Right panel: CO luminosity distributions for the same samples shown in the main panel. Horizontal dashed lines represent the mean luminosities for the PHz-IRAM sources with secure line identifications (red), and for the literature sources (black). The vertical y-axis on the right hand-side shows the molecular gas masses derived from the CO(1−0) luminosity assuming α_CO = 3.5.