Extragalactic background light models and GeV-TeV observation of blazars | ||
| NRIAG Journal of Astronomy and Geophysics | ||
| Volume 9, Issue 1, January 2020, Pages 309-320 PDF (1.2 M) | ||
| DOI: 10.1080/20909977.2020.1743468 | ||
| Authors | ||
| K. K. Singh; P. J. Meintjes | ||
| Abstract | ||
| In this work, we use two different methods to determine the opacity of the TeV gamma-rays caused by the extragalactic background light (EBL) via e—e+ production due to photon-photon interaction. The first method, Model-Dependent Approach, uses various EBL models for estimating the opacity as a function of the redshift and energy of the TeV photons. The second method, Model-Independent Approach, relies on using the simultaneous observations of blazars in the MeV-GeV energy range from the Fermi-LAT and in the TeV band from the ground-based gammaray telescopes. We make the underline assumption that the extrapolation of the LAT spectrum of blazars to TeV energies is either a good estimate or an upper limit for the intrinsic TeV spectrum of a source. We apply this method on the simultaneous observations of a few blazars at different redshifts to demonstrate a comparative study of six prominent EBL models. Opacities of the TeV photons predicted by the model-independent approach are systematically larger than the ones estimated from the modeldependent method. Therefore, the gamma-ray observations of blazars can be used to set a strict upper limit on the opacity of the Universe to the TeV photons at a given redshift. | ||
| Keywords | ||
| Galaxies: blazars; observations: gamma-rays; general: EBL | ||
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