The K-z relation for radio galaxies
The host galaxies of powerful radio sources have a fairly small scatter in luminosity, leading to a tight relationship between their near-infrared K-band magnitudes and their radio luminosities: the `K-z relation’ or `near-infrared Hubble diagram’.
We have investigated the K-z relation for a sample of over 200 radio galaxies from completely identified low-frequency selected samples with virtually complete redshift information:
