Probing of extragalactic background light with TeV gamma‐ray observations

Abstract

Extragalactic Background Light (EBL) radiation contains an information about the cosmological processes including the history of stars and galaxies formation. The detection of γ-ray sources in the energy range 0.8-40 TeV at red-shifts from z = 0.018 to z = 1.375 with SHALON telescopes led to the constraint of the EBL density, as the TeV γ-rays can be absorbed due to interaction of low-energy photons of EBL. It is compared with data from measurements and models. Also, the observations of sources with z > 2 from first and second Fermi LAT AGN catalogue have been started in the year 2014, and the first results on B2 242 + 43 (z = 2.243) and B2 0743 + 25 (z = 2.979) quasars are presented. The detection of TeV γ-ray sources at high red-shifts is the evidence of less average spectral density of EBL and thus the less star formation rate at early evolution stage than it is previously believed. K E Y W O R D S extragalactic background light, active galactic nuclei, gamma-rays

Studies of bright flat‐spectrum radio quasar 3C 454.3 at high and very‐high‐energies

“…The observed energy spectrum of 3C 454.3 in the energy range 0.8–10 TeV, is well fitted with a power law with exponential cutoff with the photon index of $$$ -1.79\pm 0.16 $$$ and $$$ {E}_{cutoff}=7.3\pm 1.9 $$$. The object EBL de‐absorbed spectrum was extracted with the extragalactic background light density from (Sinitsyna et al 2021). 3C 454.3 has been particularly bright and variable in the $$$ \gamma $$$‐ray energy range covered by Fermi LAT from 0.1–200 GeV.…”

“…Left: Spectral energy distribution of 3C 454.3 from the multi‐wavelength observations: $$$ \varDelta $$$ at TeV energies the data from SHALON observations. EBL de‐absorbed spectrum on the assumption of EBL density from Sinitsyna et al (2021) is presented with bow‐tie‐shaped area. Right: Emission map around 3C 454.3 by SHALON (color scale).…”