Astrophysics - High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
Beschreibung:
Very high energy (VHE, energy >~ 100 GeV) γ-rays originatingfrom extragalactic sources interact with low energy photons ofbackground radiation fields and produce electron-positron pairs.Alternatively, in the presence of ambient magnetic fields, they canconvert into hypothetical axion-like particles (ALPs), pseudo-scalarspin-0 bosons, predicted by extensions of the standard model. Theseparticles propagate unimpeded over cosmological distances. Here, theeffect of photon-ALP oscillations in magnetic fields of galaxy clustersand the Milky Way on VHE γ-ray spectra is studied. It is shownthat this mechanism can lead to a substantial enhancement of the VHEflux and a spectral hardening, thus effectively reducing the opacity ofthe Universe to VHE γ-rays.