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

Abstract

We study the high energy emission of two active galactic nuclei (AGNs), NGC 4258 and NGC 7213. We directly apply the general-relativistic 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 non-thermal protons to at most 10 per cent.