JVLA S and X-band Polarimetry of the Merging Cluster Abell 2256

TL;DR

This study presents JVLA polarimetry observations of the merging galaxy cluster Abell 2256, revealing highly ordered magnetic fields, significant polarized emissions, and insights into magnetic field strengths and turbulence within the cluster.

Contribution

First detailed JVLA S- and X-band polarimetry of Abell 2256, providing new measurements of magnetic field strengths and polarization properties in the cluster's radio relics.

Findings

Magnetic field strength in the relic is 1.8-5.0 microG.

High polarization (~35%) indicates ordered magnetic fields.

Depolarization models suggest turbulent magnetic components.

Abstract

We report polarimetry results of a merging cluster of galaxies Abell 2256 with Karl G. Jansky Very Large Array (JVLA). We performed new observations with JVLA at S-band (2051-3947 MHz) and X-band (8051-9947 MHz) in the C array configuration, and detected significant polarized emissions from the radio relic, Source A, and Source B in this cluster. We calculated the total magnetic field strengths toward the radio relic using revised equipartition formula, which is 1.8-5.0 microG. With dispersions of Faraday rotation measure, magnetic-field strengths toward Sources A and B are estimated to be 0.63-1.26 microG and 0.11-0.21 microG, respectively. An extremely high degree of linear polarization, as high as ~ 35 %, about a half of the maximum polarization, was detected toward the radio relic, which indicates highly ordered magnetic lines of force over the beam sizes (~ 52 kpc).The fractional polarization of the radio relic decreases from ~ 35 % to ~ 20 % around 3 GHz as the frequency decreases and is nearly constant between 1.37 and 3 GHz. Both analyses with depolarization models and Faraday tomography suggest multiple depolarization components toward the radio relic and imply the existence of turbulent magnetic fields.