The search of axion-like-particles with Fermi and Cherenkov telescopes

TL;DR

This paper explores how axion-like particles could influence gamma-ray observations from distant sources, proposing that photon-axion mixing in magnetic fields might explain spectral anomalies and guiding future searches with gamma-ray telescopes.

Contribution

It presents a comprehensive framework considering photon-axion mixing both at the source and in intergalactic space, offering new insights into gamma-ray spectra anomalies and strategies for ALP detection.

Findings

Photon-axion mixing can account for spectral puzzles in gamma-ray sources.

The framework explains the lower bounds on extragalactic background light (EBL).

Strategies for detecting ALPs with Fermi and Cherenkov telescopes are discussed.

Abstract

Axion Like Particles (ALPs), postulated to solve the strong-CP problem, are predicted to couple with photons in the presence of magnetic fields, which may lead to a significant change in the observed spectra of gamma-ray sources such as AGNs. Here we simultaneously consider in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. We show that photon/axion mixing could explain recent puzzles regarding the observed spectra of distant gamma-ray sources as well as the recently published lower limit to the EBL intensity. We finally summarize the different signatures expected and discuss the best strategy to search for ALPs with the Fermi satellite and current Cherenkov telescopes like CANGAROO, HESS, MAGIC and VERITAS.