Constraints on the Galactic Magnetic Field from the Canadian Galactic Plane Survey

TL;DR

This paper uses Canadian Galactic Plane Survey data to analyze the Galactic magnetic field's topology, providing constraints on its structure and scale height to inform models of its origin and evolution.

Contribution

It presents the highest source density of rotation measures in the Galactic disk and estimates key parameters like the RM null point and scale height, offering new constraints for magnetic field modeling.

Findings

Determined the RM null point in the outer Galaxy.

Estimated the RM scale height from CGPS data.

Provided critical constraints for large-scale magnetic field models.

Abstract

The Galactic magnetic field is important in the dynamics of our Galaxy. It is believed to play a role in star formation and influence the structure of the Galaxy. In order to understand how the Galactic magnetic field originally formed or how it is evolving, we must first determine its present topology. To this end, we have used observations from the Canadian Galactic Plane Survey (CGPS) to calculate the highest source density of rotation measures (RM) to date in the disk of the Galaxy. Using these data, we estimate the Galactic longitude of the RM null point in the outer Galaxy (where the RMs of extragalactic sources are observed to pass through zero, on average, with increasing Galactic longitude). We have also examined the RM scale height using the CGPS latitude extension. The values of these parameters offer critical constraints for modeling the large-scale magnetic field in the Galactic disk.