Notes. i = 0 is face-on and i = 90 is edge-on. The foreground extinction, A_V, is an additional parameter that we use, together with the extinction curve of Chiar & Tielens (2006), to take into account the foreground extinction from the host galaxy. These models use a standard Galactic mix of 53% silicates and 47% graphites, with maximum sizes of 0.25 μm. ${\mathrm{C}}_{\mathrm{T}}=1-{\displaystyle \int {\mathrm{e}}^{-{\mathrm{N}}_{\mathrm{LOS}}(\mathrm{i})}}\mathrm{d}\cos (\mathrm{i})$, ${\mathrm{P}}_{\mathrm{esc}}={\mathrm{e}}^{-{\mathrm{N}}_{\mathrm{LOS}}(\mathrm{i})}$, and ${\mathrm{A}}_{\mathrm{V}}^{\mathrm{LOS}}=1.086{\tau }_{\mathrm{V}}{\mathrm{N}}_{\mathrm{LOS}}(\mathrm{i})$, with ${\mathrm{N}}_{\mathrm{LOS}}(\mathrm{i})={\mathrm{N}}_0{\mathrm{e}}^{-{(90-\mathrm{i})}^2/{\sigma }^2}$. C_T is an integrated quantity (over the inclination angle, i), whilst P_esc and A_V^LOS are calculated at a given i.