The Radio Galaxy 1138-262 at Z=2.2: A Forming Cd Galaxy at the Center of a Cluster?

Abstract

Studying the morphology of high redshift radio galaxies (HZRGs) can contribute substantially to our understanding of galaxy formation and evolution in the early universe. In addition HZRGs are of exceptional interest being potential signposts for pinpointing high-redshift clusters of galaxies. It has been shown that high luminosity radio sources associated with quasars and radio galaxies in the range 0.5 < z < 1 are located in rich clusters (e.g. Hill and Lilly, 1991). At z > 2 the existence of clusters around HZRGs has not been established, but there are many indications that HZRGs may be in clusters (Dickinson, 1996 and references therein). The host galaxies of HZRGs are also the most massive galaxies known at high-redshifts, and since they are probably located in forming clusters of galaxies they are likely to be the ancestors of nearby cD galaxies. Here we report on one of the most promising objects in this respect, the radio galaxy 1138-262 at redshift 2.2.