PAH luminosity surface density as a function of stellar mass surface density, colour-coded by the mass-weighted age for each Voronoi cell (circles) and clump (stars). Only the points with an uncertainty smaller than 1 dex on each axis are shown in this image. The surface densities are computed on the sky plane, not accounting for deprojection effects. The uncertainties on the y-axis are estimated from the background standard deviation (see Sect. 3.3). On the x-axis, they come from the SED fitting confidence intervals. The diagonal lines are fit at constant sPAH for each age bin.