The Mass of Radio Galaxies from Low to High Redshift

Abstract.

Using a new radio sample, 6C* designed to find radio galaxies at z > 4 along with the complete 3CRR and 6CE sample we extend the radio galaxy K-z relation to $z \sim 4.5$. The 6C* K-z data significantly improve delineation of the K-z relation for radio galaxies at high redshift (z > 2). In a spatially flat universe with a cosmological constant ( $\rm\Omega_{\rm M}=0.3$ and $\rm\Omega_{\Lambda}=0.7$), the most luminous radio sources appear to be associated with galaxies with a luminosity distribution with a high mean ( $\approx 5L^{*}$), and a low dispersion ( $\sigma \sim 0.5$ mag) which formed their stars at epochs corresponding to $z\gtrsim 2.5$).