Spectrophotometry of a sample of 7C giant radio sources

We present spectrophotometric measurements of a sample of 7C classical double radio sources selected to have angular sizes 1.5 less than or equal to theta less than or equal to 3 arcmin and flux densities 0.4 less than or equal to S(151 MHz)less than or equal to 1.0 Jy. We find that these sources lie at redshifts out to at least 1 and have projected linear sizes approximate to Mpc. These objects provide the first evidence that giant radio sources do not become less common at high redshift, and rule out the possibility that large radio sources are confined by a medium which rapidly increases in density at high redshift. The sample provides additional support for unified schemes of powerful radio galaxies and radio quasars.