Plot of the combined data, showing the spatially resolved RC–SFR ((Σ_SFR)_RC–(Σ_SFR)_hyb) relation, for data points with spectral indices α >  −0.65 only. Panel a: results from LOFAR 140 MHz and panel b: from WSRT 1365 MHz. Each data point represents a 1.2 × 1.2 kpc² region that has been obtained from the hybrid Σ_SFR map (abscissa) and from the radio Σ_SFR map (ordinate). Shape and colour represent the different galaxies. Solid black lines show the best-fitting relation and dashed lines show the Condon relation. A 3σ cut-off was applied in all maps.