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 ≤θ≤3 arcmin and flux densities 0.4 ≤ S151 MHz ≤ 1.0 Jy. We find that these sources lie at redshifts out to at least 1 and have projected linear sizes ≈ 1 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.