Comparison of the G_UV values obtained with the Meudon PDR code and the values evaluated from the stellar composition within our FOV. Only pixels with good (S∕N > 3) detection of CO J = 7−6 are plotted. The dashed lines indicates a 1 : 1 relationship between the quantities on the axes. The uncertainties of the G_UV values derived with the Meudon PDR models are estimated with the MC experiment as discussed in Sect. 3.2. Left panel: all OB-stars are assumed to be at the center of their host star-clusters, i.e., Trumpler 14 and 16. The observed CO gas is assumed to lie on the plane perpendicular to the line of sight at a 2.35 kpc distance. Center panel: distribution of OB-stars is considered coplanar at their observed (α, δ) coordinates. The geometry of the CO gas is assumed to be coplanar as in the textitleft panel. Right panel: distribution of OB-stars is considered coplanar at their observed (α, δ) coordinates. The geometry of the CO gas is assumed as the shape indicated in Fig. 11.