A Chandra observation of the distant radio galaxy B 2 0902 + 343 : a powerful obscured active galaxy

We report a Chandra observation of the z = 3.395 radio galaxy B2 0902+343. The unresolved X-ray source is centred on the active nucleus. The spectrum is well fit by a flat power law of photon index of Γ ∼ 1.1 with intrinsic absorption of 8 × 10 22 cm −2 , and an intrinsic 2– 10 keV luminosity of 3.3 × 10 45 erg s −1. More complex models which allow for a steeper spectral index cause the column density and intrinsic luminosity to increase. The data limit any thermal luminosity of the hot magnetized medium, assumed responsible for high Faraday rotation measures seen in the radio source, to less than ∼ 10 45 erg s −1 .