Impact of oscillations of photons into axion-like particles on the very-high energy gamma-ray spectrum of the blazar PKS1424+240

Understand

Very high energy (VHE) gamma-rays undergo pair production with low energy photons of background radiation fields.

• This leads to an attenuation of the primary gamma-ray flux of extragalactic sources in the interaction with the extragalactic background light (EBL) which stretches from ultraviolet to far-infrared wavelengths.
• In the presence of magnetic fields, gamma-rays could oscillate into hypothetical axion-like particles (ALPs).
• This might lead to a reduced opacity of the Universe for VHE gamma-rays, as ALPs circumvent pair production.