Infrared-radio correlation using only the PAH component and radio continuum fluxes. Top panel: log(F_W3PAH) vs log(F_1.3 GHz) for galaxies with enough data (see text), following the legend. Error bars are shown unless smaller than the symbol. A linear fit, log(y) = m ⋅ log(x)+b, is plotted as a black line, with a shaded region indicating a 0.1 dex scatter. Bottom panel: Histogram of the squared differences between observed and fitted values.