Top: results of the fitting procedure for the diffuse component of M 33. The red filled circles are the observed fluxes for the diffuse component presented in Table 2. The best-fitting model is represented by the white dashed line while its uncertainty is defined by the gray shaded area. For clarity, errors are only shown in the bottom panel. Bottom: residuals of the fitting procedure. The red filled circles correspond to the percentage difference of the observed fluxes and the best-fitting model (white dashed line). The gray shaded area gives the uncertainty of the best-fitting model in terms of percentage.