Observational Signatures of Galactic Turbulent Dynamos

TL;DR

This study investigates the observational signatures of galactic magnetic fields generated by turbulence in the interstellar medium, focusing on Faraday rotation, synchrotron radiation, and polarization through simulations.

Contribution

It provides a self-consistent analysis of how galactic magnetic field signatures depend on turbulence, electron models, and observational parameters using MHD simulations.

Findings

RM structures are sheared and anisotropic due to differential rotation.

Synchrotron maps resemble the mean magnetic field along the line of sight.

Polarization depends strongly on frequency and resolution.

Abstract

We analyse the observational signatures of galactic magnetic fields that are self-consistently generated in magnetohydrodynamic simulations of the interstellar medium through turbulence driven by supernova (SN) explosions and differential rotation. In particular, we study the time evolution of the Faraday rotation measure (RM), synchrotron radiation, and Stokes parameters by characterising the typical structures formed in the plane of observation. We do this by defining two distinct models for both thermal and cosmic ray (CR) electron distributions. Our results indicate that the maps of RM have structures which are sheared and rendered anisotropically by differential rotation and that they depend on the choice of thermal electrons model as well as the SN rate. Synchrotron maps are qualitatively similar to the maps of the mean magnetic field along the line of sight and structures are only marginally affected by the CR model. Stokes parameters and related quantities, such as the degree of linear polarisation, are highly dependent on both frequency and resolution of the observation.