On conservative models of "the pair-production anomaly" in blazar spectra at Very High Energies

24th European Cosmic Ray Symposium

Dzhatdoev, T.A.^1

Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Leninskie gory 1-2, Moscow

119991, Russia^1

关键词: Extragalactic background light;    Gamma ray absorption;    Gamma ray sources;    Large scale structures;    Natural features;    Primary gamma rays;    Statistical significance;    Very high energies;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/632/1/012035/pdf
DOI  :  10.1088/1742-6596/632/1/012035

来源: IOP

【 摘 要 】

For some blazars, the gamma-ray absorption features due to pair-production on the Extragalactic Background Light (EBL) are fainter than expected. The present work reviews the main models that could explain this paradox, with emphasis on conservative ones, that do not include any new physics. The models that are intrinsic to the source, do allow a very hard primary spectrum, but fail to explain a regular redshift dependence of the anomaly starting energy. The model that includes a contribution from secondary photons produced by cosmic rays (CR) near the Earth seems to require a well collimated CR beam, what is hard to achieve. Finally, the model with secondary photons produced in electromagnetic (EM) cascades initiated by primary gamma-rays is considered. In principle, it allows to decrease the statistical significance of the anomaly and, while requiring quite low EGMF strength B, does not contradict to most contemporary constraints on the B value. Additionally, it is shown that the recently observed correlation between directions to hard gamma-ray sources and voids in the Large Scale Structure is a natural feature of the EM cascade model.