Comparison between the dust mass estimates when the IRAS 60 constraint is excluded or included in the fit. The left panel shows all the sky pixels, and the right panel only the f_PDR> 0 pixels. The vertical axis corresponds to the ratio of the inferred mass density of a fit without using the IRAS 60 constraint to that obtained when this constraint is present (see text). Colour corresponds to the logarithm of the density of points (see Fig. 5). The curve corresponds to the mean value.