The Radio Synchrotron Background -- A Cosmic Conundrum

TL;DR

The paper discusses the unexpectedly high diffuse radio emission background, suggesting potential unknown astrophysical sources or particle mechanisms beyond current models.

Contribution

It highlights the radio synchrotron background as a cosmic puzzle, emphasizing the need for new sources or mechanisms to explain the excess emission.

Findings

Radio background exceeds known source contributions

Current models cannot fully account for the observed emission

Suggests potential new astrophysical or particle emission mechanisms

Abstract

It has recently become apparent that the background level of diffuse radio emission on the sky is significantly higher than the level that can result from known extragalactic radio source classes or our Galaxy given our current understanding of its large-scale structure.~ In contrast to the more well-known and well-constrained cosmological and astrophysical backgrounds at microwave, infrared, optical/UV, X-ray, and gamma-ray wavelengths, this ``radio synchrotron background'' at radio wavelengths provides clear motivation for considering the possibilities of new astrophysical sources and new particle-based emission mechanisms.