Search for spectral features in extragalactic background light with gamma-ray telescopes

Understand

Cumulative optical and infrared emission from galaxies accumulated over cosmological time scales, the extragalactic background light (EBL), could be probed by complementary techniques of direct observations and source counting in the visible and infrared as well as via its imprint on the signal of distant active galactic nuclei in gamma rays.

• We compare the visible and infrared measurements with the gamma-ray constraints and study if the discrepancies of the measurements with different methods could be due to the presence of features in the EBL spectrum that are localised in the micron wavelength range.
• We combined data on time-averaged spectra of selected blazars that were obtained by Fermi and ground-based gamma-ray telescopes.
• We also modelled the effect of absorption on EBL while allowing for the existence of a previously unaccounted spectral feature.