Anisotropies in Non-Thermal Distortions of Cosmic Light from Photon-Axion Conversion

TL;DR

This paper investigates how ultralight axions interacting with photons can cause anisotropic distortions in the cosmic microwave background and produce X-ray signals in supervoids, revealing potential new signatures of dark radiation.

Contribution

It introduces a novel analysis of direction-dependent spectral distortions caused by photon-axion conversions in cosmic magnetic fields and plasma resonances.

Findings

Axion-photon mixing causes anisotropic CMB distortions.

Axions as dark radiation can produce X-ray brightening in supervoids.

Resonant conditions amplify photon-axion conversion effects.

Abstract

Ultralight axions which couple sufficiently strongly to photons can leave imprints on the sky at diverse frequencies by mixing with cosmic light in the presence of background magnetic fields. We explore such direction dependent grey-body distortions of the CMB spectrum, enhanced by resonant conditions in the IGM plasma. We also find that if such axions are produced in the early universe and represent a subdominant dark radiation component today, they could convert into X-rays in supervoids, and brighten them at X-ray frequencies.