Comparison of the ([Cii]+[Oi]63)/F_TIR and ([Cii]+[Oi]63)/ F_PAH as a function of the νF_ν(70 μm) /νF_ν(160 μm) FIR colour. The [Cii] emission has been corrected to remove the contribution originating from the ionised gas (see Sect. 3.5). Each point represents a pixel, where pixels are coloured as depicted in Fig. 2, according to their location in either the nucleus (yellow), mid-plane (green), or at increasing radial distances across in the disc (red to blue). The red solid lines represent the best linear fits to the data.