Photon-axion conversion in Active Galactic Nuclei?

TL;DR

This study investigates photon-axion conversion in AGN jets and finds it cannot occur above 100 GeV, challenging previous assumptions and suggesting potential observable effects in X-ray and soft gamma-ray bands.

Contribution

It provides a comprehensive analysis of photon-ALP conversion in AGN jets, refuting previous claims of high-energy conversion above 100 GeV.

Findings

Photon-ALP conversion cannot occur above 100 GeV in AGN jets.

This rules out a proposed method to bypass cosmic opacity at high energies.

Observable effects may appear in X-ray and soft gamma-ray bands for some AGN.

Abstract

Axion-Like Particles (ALPs) are the focus of intense current research. We analyze photon-ALP conversion in the context of relativistic jet models of Active Galactic Nuclei (AGN) for more than 100 sources. Contrary to previous claims, we find that this process cannot occur above 100 GeV regardless of the actual AGN model and the values of ALP parameters. This result rules out a proposed strategy to bypass the cosmic opacity above 100 GeV, as apparently required by observations. We also show that for some AGN an observable effect can show up in the X and soft gamma-ray bands.