A New Sample of z > 0.3 Giant Radio Galaxies from the Wenss and the First Surveys

Abstract

Giant radio galaxies (GRGs) are radio galaxies with linear sizes above 1 Mpc (H 0 = 50 km s-1 Mpc-1 assumed throughout). The aims of studying GRGs are twofold (e.g. Lacy et al. 1993, Subrahmanyan & Saripalli 1993): first, why are they so la rge? Is it because of a high age, a low density environment or a high jet power? Second, because of their large sizes, this is the only kind of radio source that can be used to probe the Intergalactic Medium (IGM) and trace its evolution. For instance, in a uniformly distributed, non-relativistic IGM, the pressure evolves as strongly as P IGM θ (1 + Z)5 (e.g. Subrahmanyan & Saripalli 1993). Collecting and studying large samples of GRGs at higher (>0.3) redshifts would be an important test for such a prediction. A first search has produced a sample of 13 0.3 < z < 1.0 GRGs (Cotter et al. 1996, hereafter CRS; Cotter et al., these proceedings), proving that these sources do indeed exist and can be found.