The luminous X-ray hotspot in 4C 74.26: synchrotron or inverse-Compton emission?

TL;DR

This paper reports the discovery of an X-ray counterpart to a radio hotspot in quasar 4C 74.26, exploring whether its emission is due to synchrotron or inverse-Compton processes, with implications for jet physics.

Contribution

It presents the first detection of an X-ray hotspot in 4C 74.26 and analyzes its emission mechanism, providing insights into jet composition and particle acceleration.

Findings

X-ray hotspot offset from radio hotspot by 19 kpc.

X-ray emission likely from synchrotron or inverse-Compton processes.

Confirmed the X-ray source as the hotspot, not a background AGN.

Abstract

We report the discovery of an X-ray counterpart to the southern radio hotspot of the largest-known radio quasar 4C 74.26 (whose redshift is z=0.104). Both XMM-Newton and Chandra images reveal the same significant (10arcsec, i.e. 19kpc) offset between the X-ray hotspot and the radio hotspot imaged with MERLIN. The peak of the X-ray emission may be due to synchrotron or inverse-Compton emission. If synchrotron emission, the hotspot represents the site of particle acceleration and the offset arises from either the jet exhibiting Scheuer's `dentist's drill' effect or a fast spine having less momentum than the sheath surrounding it, which creates the radio hotspot. If the emission arises from the inverse-Compton process, it must be inverse-Compton scattering of the CMB in a decelerating relativistic flow, implying that the jet is relativistic (Gamma >= 2) out to a distance of at least 800kpc. Our analysis, including optical data from the Liverpool Telescope, rules out a background AGN for the X-ray emission and confirms its nature as a hotspot, making it the most X-ray luminous hotspot yet detected.