SAIP2025

Compton-induced cascade $\gamma$-rays in the radio galaxy NGC 1275

Not scheduled

1h

Solomon Mahlangu House (University of the Witwatersrand, Johannesburg)

Oral Presentation Track D1 - Astrophysics Astrophysics & Space Science

Speaker

Ntshatsha Mfuphi

Description

Among the active galactic nuclei (AGNi), blazars are the brightest emitters of high- (HE, $E \ge 100\,\mathrm{MeV}$) to very-high-energy (VHE, $E \geq 100\,\mathrm{GeV}$) $\gamma$-rays from their jets. Radio galaxies, being the misaligned parent population of the blazar class, were historically not observed at these frequencies. However, there is a growing number of radio galaxies detected in HE--VHE $\gamma$-rays in recent years. In this work, we leverage and refine a Monte-Carlo photon and electron-positron ($e^\pm$) tracking code in the AGN environment of the radio galaxy NGC 1275. In the code, we consider the isotropic broad emission line and Shakura-Sunyaev (SS) accretion disk radiation fields, with mild magnetic fields in the AGN environment. We find that cascade $\gamma$-rays from the inverse-Compton scattering by relativistic $e^\pm$ pairs of these external radiation fields can explain the \emph{Fermi} Large Area Telescope’s (LAT) observation of the radio galaxy NGC 1275. We present a set of parameters obtained from the code and fit the source’s spectral energy distribution during the flaring events recorded in December 2022 and January 2023.