Fluxratios between the 150 MHz flux density and the flux densities at 250, 350, and 500 μm as a function of redshift (colour-coded by photometric or spectroscopic redshift) in ELAIS-N1. The red line shows the median flux ratios in bins of redshift (with the redshift bin width set to 0.5 at z < 3 and 1 at z > 3), and the shaded band shows the range between the 16th and 84th percentiles. The other two fields show similar patterns.