Broad-band non-thermal emission of odd radio circles induced by explosive galactic outflow remnants and their evolution.

This article focuses on explaining odd radio circles (ORCs)—recently discovered faint, ring-like radio emissions possibly linked to galaxies in dense environments—as remnants of explosive galactic outflows, termed OGREs. The authors model these OGREs as shocks driven by energetic events, likely active galactic nuclei (AGNs), that accelerate cosmic rays producing synchrotron radiation consistent with observed ORC properties such as size, spectral index, and radio power. Their calculations of broad-band spectral energy distributions (SEDs) include synchrotron, inverse Compton, bremsstrahlung, and pion-decay emissions, showing that younger OGREs have similar SEDs to older, observed ORCs if radiative cooling is effective, though younger OGREs may be rarer and harder to detect. In scenarios with inefficient radiative cooling, younger OGREs could be detectable in X-rays, potentially observable as "odd X-ray circles," offering predictions for future multi-wavelength observations to further constrain the nature of ORCs.