Gamma-rays from non-blazar AGN

Abstract

Abstract. Non-blazar Active Galactic Nuclei (AGN) have emerged as a new γ-ray emitting source class on the extragalactic sky and started to deepen our understanding of the physical processes and the nature of AGN in general. The detection of Narrow Line Seyfert 1 galaxies in the Fermi-LAT energy regime, for example, offers important information for our understanding of jet formation and radio-loudness. Radio galaxies, on the other hand, have become particularly interesting at high (HE) and very high (VHE) gamma-ray energies. With their jets not directly pointing towards us (i.e. "misaligned"), they offer a unique tool to probe into the nature of the fundamental (and often "hidden") physical processes in AGN. This review highlights and discusses some of the observational and theoretical progress achieved in the gamma-ray regime during recent years, including the evidence for unexpected spectral hardening in Centaurus A and extreme short-term variability as seen in IC 310 and M87.

Jetted Narrow-Line Seyfert 1 Galaxies & Co.: Where Do We Stand?

“…With reference to other reviews, there are many contributions by D'Ammando et al (including also some papers where NLS1s were only a section of a broader review on relativistic jets, [89,90,[140][141][142][143][144]), Ermash and Komberg [145] (general review on physical and observational properties), Boller (on history of X-ray detections [146]), and Paliya (on gamma-ray NLS1s [91]). More general reviews including sections dedicated to NLS1s were written by Rieger (gamma rays from non-blazar AGN, [147]) and Hada (high-angular resolution radio observations, [148]).…”

A search for Centaurus A-like features in the spectra of Fermi-LAT detected radio galaxies

“…According to the unified model of active galactic nuclei (AGN) (Urry & Padovani 1995), radio galaxies are radioloud AGN that have jets beamed at large inclination angles with respect to the observer's line of sight, and are therefore sometimes termed misaligned blazars. Unlike blazars, therefore, the non-thermal radiation emitted by radio galaxies is only modestly beamed (Rieger 2017). Thus radio galaxies are very interesting targets because any detected γ-ray signal from these AGN is not dominated by the highly beamed jet emission, meaning it might be possible to disentangle jet and core emission or even to detect other potential sources of γ-ray emission.…”

High-energy gamma rays and neutrinos from nearby radio galaxies

“…• Centaurus A is the nearest radio galaxy in our sample (4 Mpc), and is comparable in both size and luminosity to the Milky Way. This galaxy does not show significant evidence of variability at energies above a couple of GeV [77,78].…”

“…In this study, we focus on those radio galaxies that have been observed at TeV energies by ground-based gamma-ray telescopes (for a review of gamma-ray emission from non-blazar active galaxies, see Ref. [77]). In particular, we will consider the following list of radio galaxies (see also Table 1):…”

“…Fermi reports a high degree of variability in the emission from NGC 1275 [81]. At very high-energies, however, MAGIC reports only limited evidence of such variability [67,77,82,83].…”