XMM-Newton Observations of Three High Redshift Radio Galaxies

Abstract

We present results on the physical states of three highredshift powerful radio galaxies (3C292 atz = 0.7, 3C184 at z= 1, and 3C322 atz = 1.7). They were obtained by combining radio measurements with X-ray measurements from XMM-Newton that separate spectrally and/or spatially radio-related and hot-gas X-ray emission. Originally observed as part of a program to trace clusters of galaxies at high redshift, none of the sources is found to lie in a rich X-ray-emitting environment similar to those of some powerful radio galaxies at low redshift, although the estimated gas pressures are sufficient to confine the radio lobes. The weak gas emission is a particularly interesting result for 3C184, where a gravitational arc is seen, suggesting the presence of a very massive cluster. Here Chandra data complement the XMM-Newton measurements in spatially separating X-ray extended emission from that associated with the nucleus and rather small radio source. 3C292 is the source for which the X-ray-emitting gas is measured with the greatest accuracy, and its temperature of 2 keV and luminosity of 6.5X 1043 erg s-1are both characteristic of a poor cluster. This source allows the most accurate measurement of inverse-Compton X-ray emission associated with the radio lobes. In all structures where the magnetic-field strength can be estimated through combining measurements of radiosynchrotron and inverse-Compton X-ray emission, the field strengths are consistent with sources being in a state of minimum total energy