X-ray emission from large scale jets of AGNs at high redshifts

Abstract

The limited angular resolution of the existing telescopes, operating in radio, optical and X-ray wavebands, hinder the study on multi-spectral component (MSC) emissions from the large scale jet of AGNs. This is particularly strenuous for the sources located at high redshifts. Though a few of them were resolved in radio-optical wavebands, their X-ray counterparts have been rarely discovered. This poses a bigger challenge in understanding their emission mechanism. At high redshifts, the X-ray emission from the large scale jets are generally interpreted as inverse-Compton scattering of cosmic microwave background photons (IC/CMB), due to the increase in CMB photon density. However, recent Fermi γ-ray flux upper limit estimates on two high redshift ($z>3.5$) AGN jets (J1510+5702 and J1421-0643), question the validity of the IC/CMB model. Here, we propose a model by considering the advection of electrons from the sites of particle acceleration (Rahman et al., 2022), to interpret the MSC emission from these sources. We show that observed radio/optical/X-ray emissions can be explained by the synchrotron emission from the advected and accelerated electron distribution. We also show that the IC/CMB spectrum of this composite electron distribution satisfies the constraints drawn from Fermi observations.