a) Emission of the CO J = 3 → 2 plotted against the CO J = 2 → 1 emission. The Pearson coefficient of correlation of the data, P_c, is indicated in the lower right-hand corner. b) Emission of the continuum at 0.8 mm plotted against the 1.3 mm continuum emission. The Pearson coefficient of correlation of the data, P_c, is indicated in the lower right-hand corner. Fluxes are rescaled at 100 pc. Same symbols as for Fig. B.2.