A Unified Model for the Fan Region and the North Polar Spur: A bundle of filaments in the Local Galaxy

TL;DR

This paper proposes a unified model explaining large-scale polarized radio features as filamentary structures around the Local arm and Bubble, resolving distance contradictions and aiding understanding of the Galactic magnetic field.

Contribution

It introduces a simple, unified model for the NPS and Fan Region as local filamentary structures, unifying observations and resolving previous distance ambiguities.

Findings

Model explains large-scale polarized features as local filaments.

Consistent with multiple observational studies.

Helps understand the Galactic magnetic field contributions.

Abstract

We present a simple, unified model that can explain two of the brightest, large-scale, diffuse, polarized radio features in the sky, the North Polar Spur (NPS) and the Fan Region, along with several other prominent loops. We suggest that they are long, magnetized, and parallel filamentary structures that surround the Local arm and/or Local Bubble, in which the Sun is embedded. We show this model is consistent with the large number of observational studies on these regions, and is able to resolve an apparent contradiction in the literature that suggests the high latitude portion of the NPS is nearby, while lower latitude portions are more distant. Understanding the contributions of this local emission is critical to developing a complete model of the Galactic magnetic field. These very nearby structures also provide context to help understand similar non-thermal, filamentary structures that are increasingly being observed with modern radio telescopes.