Gamma-rays from Blazars and the Extragalactic Background Light

TL;DR

This review discusses how gamma-ray observations of blazars help constrain the diffuse Extragalactic Background Light (EBL), highlighting recent progress, remaining challenges, and future prospects especially in the multi-TeV energy range.

Contribution

It summarizes recent observational and theoretical advances in using gamma-ray data to study the EBL and discusses future improvements in the field.

Findings

Gamma-ray observations constrain EBL intensity and spectrum.

Progress made in understanding EBL's main origin.

Future multi-TeV spectra will improve EBL measurements.

Abstract

Recent observations of blazars at high energy (HE, 0.1-100 GeV) and very high energy (VHE, >0.1 TeV) have provided important constraints on the intensity and spectrum of the diffuse Extragalactic Background Light (EBL), shedding light on its main origin. Several issues remain open, however, in particular in the mid- and far-infrared bands and in the blazar emission at multi-TeV energies. This review summarizes the observational and theoretical progress in the study of the EBL with gamma-rays and the most promising future improvements, which are mainly expected from spectra in the multi-TeV range.