Hot accretion flows in low-luminosity active galactic nuclei in NGC 4258 and NGC 7213

TL;DR

This study applies a general-relativistic hot flow model to X-ray and gamma-ray data of NGC 4258 and NGC 7213, revealing insights into electron heating, magnetic fields, and proton content in low-luminosity AGN.

Contribution

It demonstrates the application of the GR hot flow model to real data, providing constraints on electron heating efficiency, magnetic field strength, and nonthermal proton content in these AGN.

Findings

10-20% of accretion power heats electrons

Flows are strongly magnetized near equipartition

Nonthermal proton content is at most 10%

Abstract

We study the high energy emission of two active galactic nuclei (AGN), NGC 4258 and NGC 7213. We directly apply the general-relativistic (GR) hot flow model, kerrflow, to the archival BeppoSAX, NuSTAR and Suzaku observations of these objects. Most of these data sets indicate that about 10-20 per cent of the accretion power is used for the direct heating of electrons, however, we find also indications for significant changes of the electron heating efficiency in some cases. Furthermore, all these X-ray data sets indicate rather strongly magnetized flows, with the magnetic field close to the equipartition with the gas pressure. Comparison of the model prediction with the Fermi/LAT data for NGC 7213 allows us to constrain the content of nonthermal protons to at most 10 per cent.