Inverse Compton X-rays from Giant Radio Galaxies at z~1
  We report XMM-Newton observations of three FR II radio galaxies at redshifts
between 0.85 and 1.34, which show extended diffuse X-ray emission within the
radio lobes, likely due to inverse-Compton up-scattering of the cosmic
microwave background. Under this assumption, through spectrum-fitting together
with archival VLA radio observations, we derive an independent estimate of the
magnetic field in the radio lobes of 3C 469.1 and compare it with the
equipartition value. We find concordance between these two estimates as long as
the turnover in the energy distribution of the particles occurs at a Lorentz
factor in excess of ~ 250. We determine the total energy in relativistic
particles in the radio emitting lobes of all three sources to range between
3e59 and 8e59 erg. The nuclei of these X-ray sources are heavily-absorbed
powerful AGN.
