A method for reconstructing the Galactic magnetic field using dispersion of fast radio bursts and Faraday rotation of radio galaxies

TL;DR

This paper introduces a method to reconstruct the Galactic magnetic field using simulated dispersion measures and Faraday rotation data from FRBs and radio galaxies, addressing extragalactic contamination and model differences.

Contribution

It presents a novel technique combining DM and RM observations to map the Galactic magnetic field and proposes improvements for real data application.

Findings

Successfully reconstructs large-scale Galactic magnetic structures

Identifies extragalactic DM as a major obstacle in accurate mapping

Provides correction methods for DM observations at high Galactic latitudes

Abstract

With the rapid increase of fast radio burst (FRB) detections within the past few years, there is now a catalogue being developed for all-sky extragalactic dispersion measure (DM) observations in addition to the existing collection of all-sky extragalactic Faraday rotation measurements (RMs) of radio galaxies. We present a method of reconstructing all-sky information of the Galactic magnetic field component parallel to the line of sight, $B_{\parallel}$, using simulated observations of the RM and DM along lines of sight to radio galaxies and FRB populations, respectively. This technique is capable of distinguishing between different input Galactic magnetic field and thermal electron density models. Significant extragalactic contributions to the DM are the predominant impediment in accurately reconstructing the Galactic DM and $\left<B_{\parallel}\right>$ skies. We look at ways to improve the reconstruction by applying a filtering algorithm on the simulated DM lines of sight and we derive generalized corrections for DM observations at $|b|$ > 10 deg that help to disentangle Galactic and extragalactic DM contributions. Overall, we are able to reconstruct both large-scale Galactic structure and local features in the Milky Way's magnetic field from the assumed models. We discuss the application of this technique to future FRB observations and address possible differences between our simulated model and observed data, namely: adjusting the priors of the inference model, an unevenly distributed population of FRBs on the sky, and localized extragalactic DM structures.