Fueling lobes of radio galaxies: statistical particle acceleration and the extragalactic gamma-ray background

TL;DR

This paper investigates how turbulent magnetic field-driven acceleration in radio galaxy lobes sustains high-energy electrons and assesses their contribution to the extragalactic gamma-ray background via inverse Compton scattering.

Contribution

It introduces a model for electron acceleration in radio galaxy lobes and evaluates their role in the diffuse gamma-ray background, linking radio galaxy physics to gamma-ray observations.

Findings

Electrons in radio galaxy lobes can reach gamma ~ 10^5 - 10^6 with turbulent magnetic fields.

The inverse Compton emission from these lobes significantly contributes to the extragalactic gamma-ray background.

The model explains observed gamma-ray emissions and predicts their impact on the gamma-ray background.

Abstract

The recent discovery of the gamma-ray emission from the lobes of the closest radio galaxy Centaurus A by Fermi implies the presence of high-energy electrons at least up to gamma ~ 10^5 - 10^6. These high-energy electrons are required to interpret the observed gamma-ray radiation in terms of inverse Compton emission off the cosmic microwave background (IC/CMB); the widely accepted scenario to describe the X-ray emission of radio galaxy lobes. In this Letter, we consider the giant radio lobes of FR II radio galaxies showing that it is possible to maintain electrons at energies gamma ~ 10^5 - 10^6, assuming an acceleration scenario (driven by turbulent magnetic fields) that compensates the radiative losses. In addition, we consider the contribution to the diffuse extragalactic gamma-ray background due to the IC/CMB emission of FR IIs' lobes showing its relevance in the keV to MeV energy range.