ar X iv : a st ro - p h / 98 01 12 8 v 2 1 8 Fe b 19 98 Radio Observations of High Redshift Radio Galaxies

We review some aspects of radio continuum polarimetric imaging of high redshift radio galaxies. The correlation between extreme values of Faraday rotation observed toward radio emitting structures in nearby radio galaxies, and X-ray emitting cluster atmospheres, is presented as a method for targeting objects at high redshift for deep X-ray searches. We present an X-ray detection of the extreme rotation measure radio galaxy PKS 1138−262 at z = 2.156, and we argue that the X-ray emission is from a cluster atmosphere with a luminosity of 1.7±0.3×10 44 h −2 ergs sec −1. We also present results on the correlation between size and redshift for a sample of ultra-luminous radio galaxies between 0 < z < 4.3. Source sizes decrease systematically with redshift, suggesting either denser environments , or younger sources, at high redshift. An alternative explanation is significant inverse Compton losses off the microwave background at high redshift.