Studying cosmological $\gamma$-ray propagation with the Cherenkov Telescope Array

TL;DR

This paper explores how the upcoming Cherenkov Telescope Array can be used to study the propagation of very-high-energy gamma rays over cosmological distances, providing insights into the extragalactic background light, intergalactic magnetic fields, and new physics beyond the Standard Model.

Contribution

It presents a first assessment of CTA's potential to investigate cosmological gamma-ray propagation effects, including EBL, IGMF, LIV, and WISPs.

Findings

CTA can effectively probe the EBL and IGMF effects on gamma-ray spectra.

The study demonstrates CTA's potential to detect signatures of physics beyond the Standard Model.

Preliminary results indicate CTA's high sensitivity will improve constraints on cosmological gamma-ray propagation models.

Abstract

The measurement of $\gamma$-rays originating from active galactic nuclei offers the unique opportunity to study the propagation of very-high-energy photons over cosmological distances. Most prominently, $\gamma$-rays interact with the extragalactic background light (EBL) to produce $e^+e^-$ pairs, imprinting an attenuation signature on $\gamma$-ray spectra. The $e^+e^-$ pairs can also induce electromagnetic cascades whose detectability in $\gamma$-rays depends on the intergalactic magnetic field (IGMF). Furthermore, physics beyond the Standard Model such as Lorentz invariance violation (LIV) or oscillations between photons and weakly interacting sub-eV particles (WISPs) could affect the propagation of $\gamma$-rays. The future Cherenkov Telescope Array (CTA), with its unprecedented $\gamma$-ray source sensitivity, as well as enhanced energy and spatial resolution at very high energies, is perfectly suited to study cosmological effects on $\gamma$-ray propagation. Here, we present first results of a study designed to realistically assess the capabilities of CTA to probe the EBL, IGMF, LIV, and WISPs.