Broadband Modeling of Low Luminosity Active Galactic Nuclei Detected in Gamma Rays

TL;DR

This study models the broadband emission of four low luminosity active galactic nuclei detected in gamma rays, exploring their jet structures and emission mechanisms across multiple wavelengths to understand high-energy gamma-ray origins.

Contribution

It introduces a comprehensive multi-wavelength modeling approach for low luminosity AGNs, highlighting the potential role of kilo-parsec scale jets in gamma-ray production.

Findings

Synchrotron and SSC models fit radio to gamma-ray data up to certain energies.

Higher energy gamma rays may originate from kilo-parsec scale jets via inverse Compton scattering.

Host galaxy emission is significant for gamma-ray production in these sources.

Abstract

Low luminosity active galactic nuclei are more abundant and closer to us than the luminous ones but harder to explore as they are faint. We have selected the four sources NGC 315, NGC 4261, NGC 1275, and NGC 4486, which have been detected in gamma rays byFermi-LAT. We have compiled their long-term radio, optical, X-ray data from different telescopes, analysed XMM-Newton data for NGC 4486, XMM-Newton and Swift data for NGC 315. We have analysed the Fermi-LAT data collected over the period of 2008 to 2020 for all of them. Electrons are assumed to be accelerated to relativistic energies in sub-parsec scale jets, which radiate by synchrotron and synchrotron self-Compton emission covering radio to gamma-ray energies. This model can fit most of the multi-wavelength data points of the four sources. However, the gamma-ray data points from NGC 315 and NGC 4261 can be well fitted only up to 1.6 GeV and 0.6 GeV, respectively in this model. This motivates us to find out the origin of the higher energy {\gamma}-rays detected from these sources. Kilo-parsec scale jets have been observed previously from these sources in radio and X-ray frequencies. If we assume {\gamma}-rays are also produced in kilo-parsec scale jets of these sources from inverse Compton scattering of starlight photons by ultra-relativistic electrons, then it is possible to fit the gamma-ray data at higher energies. Our result also suggests that strong host galaxy emission is required to produce GeV radiation from kilo-parsec scale jets.