A homogeneous data set of infrared observations of 83 3CR galaxies with redshifts 0<z<1.6, selected from a statistically complete sample of 90 radio sources, is used to study the colours and magnitudes of these galaxies as a function of their redshifts. New infrared observations are presented for 66 radio galaxies, in addition to new optical results obtained from a re-analysis of existing CCD images. It is shown that the infrared colours do not deviate from the predicted relations with redshift for a standard giant elliptical galaxy spectrum, indicating that the Giant Branch is basically unchanged at redshifts of unity. The optical to infrared colours, however, show substantial deviations at high redshift. No galaxies have been found that are significantly redder than a passively evolving galaxy, and there is a significant scatter of colours bluewards from this model. The excess of ultraviolet light responsible for these colours is not concentrated at the nucleus, and is interpreted as resulting from bursts of star formation throughout the galaxy that may be associated with the radio activity. The ultraviolet excess is correlated with the line strength of the narrow emission lines. If q0∼0.5, the infrared Hubble diagram shows substantial luminosity evolution amounting to a change in absolute magnitude of about a magnitude at z = 1. This change may be completely accounted for by the passive evolution of the stellar population of the radio galaxies.
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Lilly et al. (1984) studied this question.