MH_2,total/MH_2,CO versus [C II]/CO(l–0) for single component models (left), multi-component models (middle), and power law models (right). The shades and symbols are described in Fig. 4. The dashed gray lines corresponds to the relation from M2O while the dashed red lines show the linear regressions fitted to the combined posterior distribution for the entire sample. We indicate the equations of linear regressions fitted to the 2D-PDF of the whole sample and the associated coefficients of determination R².