Integrated dust and PAH emission SEDs for the diffuse component, for model galaxies with different levels of SFR (plotted as different curves in each panel). All models shown in this figure are for pure disk galaxies (B/D = 0.0). From left to right the panels show model galaxies with various levels of contribution from the old stellar populations (old = 0.1, old = 2.0 and old = 20.0). From top to bottom the panels show models with various face-on B band opacities (, , and ). The colour coding is as follows: green is for SFR′ = 0.0   M_⊙/yr, red is for SFR′ = 2.0   M_⊙/yr, blue is for SFR′ = 10.0   M_⊙/yr and black is for SFR′ = 20.0   M_⊙/yr.