Extended X-ray emission from the z=4.26 radio galaxy 4C 63.20

TL;DR

This study presents deep Chandra X-ray observations of the high-redshift radio galaxy 4C 63.20, revealing extended X-ray emission likely from lobes affected by inverse Compton scattering off the CMB, supporting models of lobe evolution at high redshift.

Contribution

First detailed X-ray imaging of a z>3.5 radio galaxy showing extended emission consistent with inverse Compton processes in lobes.

Findings

X-ray emission is resolved into a core and off-nuclear sources.

The X-ray and radio data support a jet model with IC/CMB as the X-ray origin.

Supports the idea that IC/CMB affects high-redshift radio lobe visibility.

Abstract

We report on deep Chandra X-ray Telescope imaging observations of 4C 63.20, one of the few known radio galaxies at z>3.5. The X-ray counterpart is resolved into a core plus two off-nuclear sources that (combined) account for close to 30% of the total X-ray flux. Their morphology and orientation are consistent with a diffuse, lobe-like nature, albeit compact hotspots cannot be ruled out. The broadband spectral energy distribution of 4C 63.20 can be reproduced with a jet model where the majority of the radio flux can be ascribed to synchrotron emission from the hotspots, whereas the (non-nuclear) X-ray emission is produced via Inverse Compton (IC) off of Cosmic Microwave Background (CMB) photons within the extended lobes. This scenario is broadly consistent with the expectation from highly magnetized lobes in a hotter CMB, and supports the view that IC/CMB may quench less extreme radio lobes at high redshifts.