Pearson correlation coefficient r of the T_dust − Σ_SFR relation vs that of the T_dust − Σ_M* relation. AGN galaxies are marked with stars, non-AGN galaxies with circles. The galaxies are colour-coded according to the p-values of the χ² test (see Sect. 3.3.2): blue symbols to p < 0.05 (aligned with the young star-driven heating assumption: YS) and orange symbols correspond to p ≥ 0.05 (deviation from the young star heating assumption: not YS). The black dashed line represents the 1:1 relation. The grey histograms in the margins show the distributions of the correlation coefficients for T_dust − Σ_SFR (top) and T_dust − Σ_M* (right).