A complete sample of radio sources in the North Ecliptic Cap, selected at 38MHz - III. Further imaging observations and the photometric properties ofthe sample

Further imaging observations of a sample of radio sources in the North Ecli ptic Cap are presented and a number of new identifications are made. Using redshifts from spectroscopic data presented in a companion paper by Lacy et al,,:the photometric properties of the galaxies in the sample are discusse d. It is shown that: (1) out to at least z approximate to 0.6 radio galaxie s are good standard candles irrespective of radio luminosity; (2) for 0.6 l ess than or similar to z less than or similar to 1 a large fraction of the sample has magnitudes and colours consistent with a non-evolving giant elli ptical, and (3) at higher redshifts, where the R-band samples the rest-fram e UV flux, most objects have less UV luminosity than expected if they form their stellar populations ata constant rate from a high redshift to z simil ar to 1 in unobscured star-forming regions (assuming an Einstein-de Sitter cosmology). The consequences of these observations are briefly discussed.