JVLA S- and X-b and polarimetry of the merging cluster Abell 2256

Abstract

We report on polarimetry results of a merging cluster of galaxies, Abell 2256, with the Karl G. Jansky Very Large Array (JVLA). We performed new observations with JVLA at the S b and (2051-3947 MHz) and X b and (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 μG. With dispersions of Faraday rotation measure, the magnetic-field strengths toward Sources A and B are estimated to be 0.63-1.26 μG and 0.11-0.21 μG, 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% at 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.