Top: stellar mass density profile (points) computed on the basis of the surface brightness profiles (see Sect. 5.1.3). The error-bars indicate a factor two. Many uncertainties affect this profile such as the photometric errors, but also the model-dependent fit assuming a family of star-formation history, or an initial stellar mass function, so the factor of two is purely illustrative. Bottom: gas column density profile (points), converted from HI by multiplying by a factor 1.4 from Lelli et al. (2010). Error-bars are not provided by Lelli et al. (2010) so a 10% uncertainty has been assumed. The shaded area indicates the regions excluded for the fit (based on the bulge and bumps observed in the photometric profiles) but the model is in agreement with the data also in the remaining of the disk. In both panels, the red dashed lines indicates our best model profile.