CO(3−2) line luminosity as a function of total infrared luminosity of PONOS, obtained with the different models, compared with observational data. Symbols and colour-coding are as in Fig. 15. The SM was not included because of its very low CO luminosity. Due to the scarcity of observations CO(3−2) data at z ≳ 6, most data shown in this figure (except for Strandet et al. 2017 at z = 6.9) represent galaxies at z = 1 − 4: Gowardhan et al. (2019) at z ∼ 3.2, Tacconi et al. (2013) at z = 1 − 3, Daddi et al. (2015) at z = 1.5, Yang et al. (2017) at z = 2 − 4, Circosta et al. (2021) at z = 2 − 2.5 and Zanella et al. (2023) at z ∼ 1.