Spatially resolved relations with cosmic-ray transport accounted for between the magnetic field strength and the SFR surface density (a) and with the combined atomic and molecular gas mass surface density (b). The Σ_SFR and the Σ_{H I + H2} maps have been smoothed with a Gaussian kernel in order to account for cosmic-ray transport. Data points are coloured according to the radio spectral index and, in panel (b), according to the point density. Best-fitting relations are shown as sold lines and the theoretical expectations as dashed lines.