Blazar jets as possible sources of ultra-high energy photons: a short review

TL;DR

This review discusses the potential of blazar jets, powered by supermassive black holes, to produce ultra-high energy photons through particle acceleration and hadronic processes, supported by recent neutrino and gamma-ray observations.

Contribution

It provides a qualitative overview of mechanisms in blazars that could generate ultra-high energy photons, highlighting recent observational evidence and theoretical models.

Findings

IceCube neutrino detection coincides with gamma-ray emission from blazar TXS 0506+056

Blazar jets can accelerate particles to EeV energies via shocks and magnetic reconnection

Hadronic models are supported by gamma-ray and neutrino observations

Abstract

In this work, I present a qualitative discussion on the prospect of production of ultra-high photons in blazars. The sources are a subclass of active galactic nuclei which host supermassive black holes and fire relativistic jets into the intergalactic medium. The kpc scale jets are believed to be dominated by Poynting flux and constitute one of the most efficient cosmic particle accelerators, that potentially are capable of accelerating the particles up to EeV energies. Recent IceCube detection of astrophysical neutrino emission in coincidence with the enhanced gamma-ray from Tev blazar TXS 0506 + 056 further supports hadronic models of blazar emissions in which particle acceleration processes such as relativistic shocks, magnetic re-connection, and relativistic turbulence could energize hardrons, e. g. protons, up to energies equivalent to billions of Lorentz factors. The ensuing photo-pionic processes may then result in gamma-rays accompanied by neutrino flux. Furthermore, the fact that blazars are the dominant source of observed TeV emission encourages us to search for signatures of acceleration scenarios that would lead to the creation of ultra-high energy photons.