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ABSTRACT Very high energy (VHE) γ-rays ($$\gtrsim\!\! 0.1\rm ~TeV$$) and neutrinos are crucial for identifying accelerators of ultra-high-energy cosmic rays (UHECRs), but this is challenging especially for UHECR nuclei. In this work, we develop a numerical code to solve the transport equation for UHECRs and their secondaries, where both nuclear and electromagnetic cascades are taken into account self-consistently, considering steady UHECR accelerators such as radio galaxies. In particular, we focus on Centaurus A, which has been proposed as one of the most promising UHECR sources in the local Universe. Motivated by observations of extended VHE γ-ray emission from its kiloparsec-scale jet by the High Energy Stereoscopic System (H.E.S.S.), we study interactions between UHECRs accelerated in the large-scale jet and various target photon fields including blazar-like beamed core emission, and present a quantitative study on VHE γ-ray signatures of UHECR nuclei, including the photodisintegration and Bethe–Heitler pair production processes. We show that VHE γ-rays from UHECR nuclei could be detected by the ground-based γ-ray telescopes given that the dominant composition of UHECRs consists of intermediate-mass (such as oxygen) nuclei.
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High-energy Neutrino Emission from Espresso-reaccelerated Ions in Jets of Active Galactic Nuclei
Abstract We present a bottom-up calculation of the flux of ultrahigh-energy cosmic rays (UHECRs) and high-energy neutrinos produced by powerful jets of active galactic nuclei (AGNs). By propagating test particles in 3D relativistic magnetohydrodynamic jet simulations, including a Monte Carlo treatment of sub-grid pitch-angle scattering and attenuation losses due to realistic photon fields, we study the spectrum and composition of the accelerated UHECRs and estimate the amount of neutrinos produced in such sources. We find that UHECRs may not be significantly affected by photodisintegration in AGN jets where theespressomechanism efficiently accelerates particles, consistent with Auger’s results that favor a heavy composition at the highest energies. Moreover, we present estimates andupper boundsfor the flux of high-energy neutrinos expected from AGN jets. In particular, we find that (i) source neutrinos may account for a sizable fraction, or even dominate, the expected flux of cosmogenic neutrinos; (ii) neutrinos from theβ-decay of secondary neutrons produced in nucleus photodisintegration end up in the teraelectronvolt to petaelectronvolt band observed by IceCube, but can hardly account for the observed flux; (iii) UHECRs accelerated via theespressomechanism lead to nearly isotropic neutrino emission, which suggests that nearby radio galaxies may be more promising as potential sources. We discuss our results in light of multimessenger astronomy and current/future neutrino experiments.
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- PAR ID:
- 10390031
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 942
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 37
- Size(s):
- Article No. 37
- Sponsoring Org:
- National Science Foundation
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