On conservative models of “the pair-production anomaly” in blazar spectra at Very High Energiesстатья
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Дата последнего поиска статьи во внешних источниках: 22 ноября 2015 г.
Аннотация: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.