Active Galactic Nuclei as High-Energy Neutrino Sources

Abstract

Active galactic nuclei (AGN) are believed to be promising candidates of extragalactic cosmic-ray accelerators and sources, and associated high-energy neutrino and hadronic gamma-ray emission has been studied for many years. We review models of high-energy neutrino production in AGN and discuss their implications for the latest IceCube observation of the diffuse neutrino intensity.

Cosmic tau neutrino detection via Cherenkov signals from air showers from Earth-emerging taus

“…The tau energy fraction upon exit depends on both the energy of the initial tau neutrino and the angle. For example, for β tr = 20 • , the typical tau energy fraction is a few per cent of the tau neutrino energy for E ν = 10 9 GeV, but only a few tenths of a percent for E ν = 10 10 GeV, even though the overall tau exit probabilities for these two energies differ by less than a factor of 2. Tables of tau exit probabilities and the relative probability for an exiting tau with energy E τ given the incident neutrino energy E ντ and angle β tr are used in the Monte Carlo evaluation of the aperture and sensitivity independent of neutrino flux.…”

“…A neutrino event detected by IceCube that appears correlated at 3σ with gamma-flaring data from an active galactic nuclei source has been reported [6]. Gamma ray bursts [7], newborn pulsars [8], active galactic nuclei [9], galactic clusters with central sources [10,11] and UHECR photodisintegration within cosmic ray sources [12] are among candidates sources for the diffuse astrophysical flux of neutrinos. Astrophysical neutrinos are key to the multi-messenger approach to understand sources of cosmic radiation [13].…”

“…[8]. The dark blue curve labeled AGN is a prediction from active galactic nuclei sources [9]. Neutrinos from galactic clusters with central sources [10,11] are shown with the light blue curve.…”

“…In addition to computing the energy-dependent aperture and sensitivity, we also calculate the event rate for a given flux of tau neutrinos above a specified energy. We follow the same procedure as for the flux independent [8], AGNs [9], galactic clusters with central sources [10,11], late flares and prompt emission from GRBs [7] and from UHECR photodisintegration within a source (labeled UFA) [12]. Observational sensitivities are shown as in Fig.…”

Patterns in the Multiwavelength Behavior of Candidate Neutrino Blazars

“…Among the prime candidates are active galactic nuclei (AGN), especially those with a relativistic jet pointing towards us, socalled blazars (e.g. Stecker et al 1991;Mannheim et al 1992;Mannheim 1993;Szabo & Protheroe 1994;Mannheim 1995;Mastichiadis 1996;Protheroe 1999;Atoyan & Dermer 2001;Dimitrakoudis et al 2012;Murase 2017). No significant clusters of neutrinos in either space or time have been identified by all-sky searches of IceCube data (Aartsen et al 2017a;Aartsen et al 2015;Aartsen et al 2020).…”