Influence of the density distribution in the local ISM (silicates with a 5 nm thick mantle and carbons with a 20 nm thick mantle). Cold neutral medium (CNM) with n_H = 25 to 70 H/cm³ is shown in pink, CNM with n_H = 100 H/cm³ surrounded by Warm Neutral Medium (WNM) with n_H = 1 H/cm³ is plotted in yellow, and WNM with n_H = 1 H/cm³ is displayed in turquoise. The three models overlap in the figures. The radiation field is also varied with . In panels d), e), and f), seven lines of the same colour are plotted. Each of these lines corresponds to a different value of G₀. For instance, in panel f), the turquoise lines from left to right correspond to G₀ = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, and 1.4, respectively. The models falling below the observed E(B − V) to ℛ ratio are those illuminated by an ISRF scaled with G₀ = 1.3 and 1.4. See Sect. 2.2 for description of the black and white lines and symbols.