Diffuse cluster-like radio emission in poor environments

TL;DR

This study investigates a diffuse radio source with two components in a poor environment, revealing potential relics and filament associations, and emphasizes the role of synchrotron radiation in low-density cosmic structures.

Contribution

It provides a detailed multi-wavelength analysis of a unique diffuse radio source in a poor environment, suggesting possible origins and highlighting the importance of synchrotron emission in such settings.

Findings

Northern component is a likely radio relic in a poor galaxy cluster.

Southern component aligns with a galaxy filament at z~0.04.

The source demonstrates the utility of synchrotron radiation in low-density environments.

Abstract

We present a study of the spectral, polarimetric, morphological and environmental properties of the diffuse radio source 0809+39 using observations taken with the Westerbork Synthesis Radio Telescope, the Very Large Array, and archival optical and X-ray data. The source has two distinct diffuse, steep-spectrum components, one in the north that is highly polarized, and a linear southern component undetected in polarization. We discuss several plausible origins for each component, and conclude that the northern bright polarized component is most likely a radio relic associated with a poor z$\sim$0.2 cluster of galaxies, with a radio/X-ray luminosity ratio two orders of magnitude above typical values. The southern component is aligned with a more extended filament of galaxies $\sim$5 Mpc long at z$\sim$0.04. Deep optical and X-ray follow-ups are still needed in order to confirm and understand the physical origins of the synchrotron emission. Whatever the details of these origins, 0809+39 highlights the utility of synchrotron radiation for illuminating the diffuse components of low density environments unrelated to rich clusters.