Gamma-ray cosmology and fundamental physics with TeV blazars: results from 20 years of observations

TL;DR

This study analyzes 20 years of TeV blazar gamma-ray data to explore cosmic photon fields, universe expansion, and fundamental physics, providing new constraints on the extragalactic background light, Hubble constant, and Lorentz-invariance violation.

Contribution

It presents the most comprehensive gamma-ray spectral analysis from TeV blazars to date, constraining key cosmological and fundamental physics parameters.

Findings

Constructed the extragalactic background light spectrum from gamma-ray data.

Measured the Hubble constant consistent with other methods.

Constrained Lorentz-invariance violation energy scale to be above 60% of the Planck scale.

Abstract

Gamma rays from TeV blazars have been detected by ground-based experiments for more than two decades. We have collected the most extensive set of archival spectra from these sources in order to constrain the processes affecting gamma-ray propagation on cosmological distances. We discuss our results on the diffuse photon field that populates universe, called the extragalactic background light, on the expansion rate of the Universe, and on fundamental physics in the form of axion-like particles and Lorentz-invariance violation. Specifically, we present a spectrum of the extragalactic background light from 0.26 to 105 microns constructed from the gamma-ray observations, we measure a value of the Hubble constant compatible with other estimates, and we constrain the energy scale at which Lorentz-invariance violation impacts gamma-ray absorption by the extragalactic background light to be larger than sixty percent of the Planck scale.