Chandra measurements of 3 C 220 . 1 ’ s X - ray core and cluster

We report results of an 18 ks exposure with the ACIS instrument on Chandra of the powerful z = 0.62 radio galaxy 3C 220.1. The X-ray emission separates into cluster gas of emission-weighted kT ∼ 5 keV and 0.7-12 keV luminosity (to a radius of 45 arcsec) 5.6 × 10 44 ergs s −1 , and unresolved emission (coincident with the radio core). While the extended X-ray emission is clearly thermal in nature, a straightforward cooling-flow model, even in conjunction with a point-source component, is a poor fit to the radial profile of the X-ray emission. This is despite the fact that the measured properties of the gas suggest a massive cooling flow of ∼ 130 M ⊙ yr −1 , and the data show weak evidence for a temperature gradient. The central unresolved X-ray emission has a power-law spectral energy index α ∼ 0.7 and 0.7-12 keV luminosity 10 45 ergs s −1 , and any intrinsic absorption is relatively small. The two-point spectrum of the core emission between radio and X-ray energies has α rx = 0.75. Since this is a flatter spectrum than seen in other sources where the X-ray emission is presumed to be radio-related, regions close to the AGN in this source may dominate the central X-ray output, as is believed to be the case for lobe-dominated quasars. Simple unification models would be challenged if this were found to be the case for a large fraction of high-power radio galaxies.