Depolarization of synchrotron radiation in a multilayer magneto-ionic medium

TL;DR

This paper develops extended analytical formulas for depolarization of synchrotron radiation in multilayer magneto-ionic media, and applies them to observational data from galaxy M51 to disentangle depolarization effects.

Contribution

It introduces new depolarization equations for multilayer systems including internal Faraday dispersion, aiding interpretation of radio polarization data.

Findings

Effective multiwavelength observational constraints on depolarization scenarios.

Explicit depolarization formulas for two- and three-layer systems.

Application to M51 demonstrates disentangling line-of-sight depolarization contributions.

Abstract

Depolarization of diffuse radio synchrotron emission is classified in terms of wavelength-independent and wavelength-dependent depolarization in the context of regular magnetic fields and of both isotropic and anisotropic turbulent magnetic fields. Previous analytical formulas for depolarization due to differential Faraday rotation are extended to include internal Faraday dispersion concomitantly, for a multilayer synchrotron emitting and Faraday rotating magneto-ionic medium. In particular, depolarization equations for a two- and three-layer system (disk-halo, halo-disk-halo) are explicitly derived. To both serve as a `user's guide' to the theoretical machinery and as an approach for disentangling line-of-sight depolarization contributions in face-on galaxies, the analytical framework is applied to data from a small region in the face-on grand-design spiral galaxy M51. The effectiveness of the multiwavelength observations in constraining the pool of physical depolarization scenarios is illustrated for a two- and three-layer model along with a Faraday screen system for an observationally motivated magnetic field configuration.