Puzzling large-scale polarization in the galaxy cluster Abell 523

TL;DR

This study presents the first detection of large-scale polarized emission in the galaxy cluster Abell 523, revealing filamentary magnetic structures on scales of about 2.5 Mpc through advanced radio observations and simulations.

Contribution

It provides the first evidence of polarized emission on large scales in Abell 523, linking it to peripheral radio halo filaments using combined multi-instrument data and simulations.

Findings

Detection of polarized emission on ~2.5 Mpc scales

Polarized filaments are located in the cluster outskirts

Total intensity emission is limited to the central region

Abstract

Large-scale magnetic fields reveal themselves through diffuse synchrotron sources observed in galaxy clusters such as radio halos. Total intensity filaments of these sources have been observed in polarization as well, but only in three radio halos out of about one hundred currently known. In this paper we analyze new polarimetric Very Large Array data of the diffuse emission in the galaxy cluster Abell 523 in the frequency range 1-2 GHz. We find for the first time evidence of polarized emission on scales of ~ 2.5 Mpc. Total intensity emission is observed only in the central part of the source, likely due to observational limitations. To look for total intensity emission beyond the central region, we combine these data with single-dish observations from the Sardinia Radio Telescope and we compare them with multi-frequency total intensity observations obtained with different instruments, including the LOw Frequency ARray and the Murchison Widefield Array. By analysing the rotation measure properties of the system and utilizing numerical simulations, we infer that this polarized emission is associated with filaments of the radio halo located in the outskirts of the system, in the peripheral region closest to the observer.