The X‐Ray–Radio Alignment in thez = 2.2 Radio Galaxy PKS 1138−262

Abstract

We present high resolution X-ray observations of the narrow line radio galaxy PKS 1138-262 at z = 2.156 with the ACIS-S detector on the Chandra observatory. These observations show that the X-ray emission from 1138-262 is dominated by emission from the AGN with a (rest frame) 2 to 10 keV luminosity of 4x10^{45} erg/s. The relative X-ray and radio properties of the AGN in 1138-262 are similar to those seen for the AGN in the archetype powerful radio galaxy Cygnus A. Between 10% and 25% (depending on energy) of the X-ray emission from 1138--262 is spatially extended on scales of 10'' to 20''. The extended X-ray emission is elongated, with a major axis aligned with that of the radio source. While the X-ray and radio emissions are elongated on similar scales and position angles, there is no one-to-one correspondence between the radio and X-ray features in the source. The most likely origin for the extended X-ray emission in 1138-262 is thermal emission from shocked gas, although we cannot rule-out a contribution from inverse Compton emission. If the emission is from hot gas, the gas density is 0.05 cm^{-3} and the gas mass is 2.5x10^{12} M_solar. The pressure in this hot gas is adequate to confine the radio emitting plasma and the optical line emitting gas. We set an upper limit of 1.5x10^{44} erg/s to the 2 to 10 keV luminosity of any normal cluster atmosphere associated with 1138-262. No emission was detected from any of the Ly alpha emitting galaxies in the (proto-) cluster around 1138-262, outside of the Ly alpha halo of 1138-262 itself, to a 2 to 10keV luminosity limit of 1.2x10^{43}erg/s.