The VHE anomaly in blazar spectra and related phenomena

Abstract

Most of the recent research on extragalactic $\gamma$-ray propagation focused on the study of the $\gamma \gamma \to e^{+}{e}^{-}$ absorption process ("absorption-only model"). Starting from a possible anomaly at very high energies (VHE, E >100 GeV), we briefly review several existing deviations from this model. The exotic interpretation of the VHE anomaly is not supported by the recent works. On the other hand, the process of intergalactic electromagnetic cascade development naturally explains these effects. We discuss phenomenology of intergalactic cascades and the main spectral signatures of the electromagnetic cascade model. We also briefly consider the hadronic cascade model; it also may explain the data, but requires low strength of magnetic field around the source of primary protons or nuclei.

arXiv commentProc. ISVHECRI-2016 conference, Moscow (2016), 6 pages, 14 figures

References in corpus (22)

• Evidence for strong extragalactic magnetic fields from Fermi observations of TeV blazars
• Semi-analytic modeling of the EBL and consequences for extragalactic gamma-ray spectra
• An improved limit on the axion-photon coupling from the CAST experiment
• Search for Spectral Irregularities due to Photon-Axionlike-Particle Oscillations With the Fermi Large Area Telescope
• Insights Into the High-Energy Gamma-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era
• Time Delay of Cascade Radiation for TeV Blazars and the Measurement of the Intergalactic Magnetic Field
• Very High Energy Gamma-Rays from AGN: Cascading on the Cosmic Background Radiation Fields and the Formation of Pair Halos
• First lower limits on the photon-axion-like particle coupling from very high energy gamma-ray observation
• Hints of the existence of Axion-Like-Particles from the gamma-ray spectra of cosmological sources
• Indications for a pair-production anomaly from the propagation of VHE gamma-rays
• Role of line-of-sight cosmic ray interactions in forming the spectra of distant blazars in TeV gamma rays and high-energy neutrinos
• Secondary photons and neutrinos from cosmic rays produced by distant blazars
• Evidence for GeV Pair Halos around Low Redshift Blazars
• High energy electromagnetic cascades in extragalactic space: physics and features
• A Three-Year Multi-Wavelength Study of the Very High Energy Gamma-ray Blazar 1ES 0229+200
• ELMAG: A Monte Carlo simulation of electromagnetic cascades on the extragalactic background light and in magnetic fields
• On the origin of highest energy gamma-rays from Mkn 501
• Very hard gamma-ray emission from a flare of Mrk 501
• Blazar halos as probe for extragalactic magnetic fields and maximal acceleration energy
• On the hadronic cascade scenario for extreme BL Lacs
• A Correlation Between Hard Gamma-ray Sources and Cosmic Voids Along the Line of Sight
• On conservative models of "the pair-production anomaly" in blazar spectra at Very High Energies