The nature of the 3CR radio galaxies at z=1

Best, P. N.; Longair, M. S.; R"ottgering, H. J. A.

The nature of the 3CR radio galaxies at z=1

Authors

Best, P. N.

Longair, M. S.

R"ottgering, H. J. A.

Description

We present evidence that the 3CR radio galaxies at redshift one are already very massive, highly dynamically evolved galaxies, which lie at the heart of (proto--)cluster environments. Since nearby 3CR double radio sources are generally found in more isolated surroundings, the galactic environments of these galaxies must change dramatically with redshift. Therefore, the original `uniform population, closed box' interpretation of the infrared K--magnitude vs redshift relationship no longer appears valid. We propose a new interpretation: the powerful radio galaxies selected at high and low redshift have different evolutionary histories, but must contain a similar mass of stars, a few times 10-to-the-power-11 solar masses, and so conspire to produce the `passively evolving' K-z relation observed. We discuss this model in the context of the current understanding of powerful radio sources and, in light of this new model, we compare the K-z relation of the 3CR galaxies with those derived for lower power radio galaxies and for brightest cluster galaxies.
12 pages including 4 figures. LaTeX, using knawproc.cls. To appear in proceedings of `The most distant radio galaxies', Amsterdam, 15-17th October 1997