Detection of distant AGN by MAGIC: the transparency of the Universe to high-energy photons

TL;DR

This paper explains how photon oscillations into axion-like particles in extragalactic magnetic fields can account for the universe's unexpected transparency to high-energy gamma rays, supported by recent blazar observations.

Contribution

It introduces a novel explanation involving axion-like particles for the universe's transparency to gamma rays, reconciling observations with standard blazar emission models.

Findings

Detection of blazar 3C279 supports increased universe transparency.

Photon-axion oscillations can explain gamma-ray spectra.

Predictions testable by current and upcoming gamma-ray detectors.

Abstract

The recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided photon oscillations into a veri light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect explains the observed spectrum of 3C279. Our prediction can be tested in the near future by the satellite-borne GLAST detector as well as by the ground-based Imaging Atmospheric Cherenkov Telescpoes H.E.S.S., MAGIC, CANGAROO III, VERITAS and by the Extensive Air Shower arrays ARGO-YBJ and MILAGRO.