Gamma-ray emitting radio galaxies at hard X-rays: Seyfert core or jet emission?

TL;DR

This study analyzes gamma-ray emitting radio galaxies to determine whether their hard X-ray emissions originate from jets or accretion disks, revealing diverse emission mechanisms across different sources.

Contribution

It provides a combined X-ray and gamma-ray analysis of radio galaxies, identifying varied origins of hard X-ray emission, including jet, Seyfert core, or a mix of both.

Findings

M 87's X-ray emission is jet-dominated.

Cen A's X-ray emission is from the Seyfert core.

3C 111 shows combined jet and Seyfert core emission.

Abstract

A number of radio galaxies has been detected by Fermi/LAT in the gamma-ray domain. In some cases, like Cen A and M 87, these objects have been seen even in the TeV range by Cherenkov telescopes. Whereas the gamma-ray emission is likely to be connected with the non-thermal jet emission, dominating also the radio band, the situation is less clear at hard X-rays. While the smoothly curved continuum emission and the overall spectral energy distribution indicate a non-thermal emission, other features such as the iron line emission and the low variability appear to be rather of Seyfert type, i.e. created in the accretion disk and corona around the central black hole. We investigate several prominent cases using combined X-ray and gamma-ray data in order to constrain the possible contributions of the jet and the accretion disk to the overall spectral energy distribution in radio galaxies. Among the three sources we study, three different origins of the hard X-ray flux can be identified. The emission can be purely non-thermal and caused by the jet, as in the case of M 87, or thermal inverse Compton emission from the Seyfert type core (Cen A), or appears to be a superposition of non-thermal and thermal inverse Compton emission, as we observe in 3C 111. Gamma-ray bright radio galaxies host all kinds of AGN cores, Seyfert 1 and 2, BL Lac objects, and also LINER.