Using low-frequency pulsar observations to study the 3-D structure of the Galactic magnetic field

TL;DR

This paper demonstrates how low-frequency pulsar observations, using dispersion and Faraday rotation measurements, can effectively map the three-dimensional structure of the Galactic magnetic field, especially in the halo region.

Contribution

It introduces new low-frequency RM and DM catalogues from LOFAR and MWA, enhancing understanding of the GMF's 3D structure and supporting future SKA studies.

Findings

RM catalogues corrected for ionospheric effects

Improved mapping of the Galactic halo magnetic field

Progress towards SKA's magnetic field studies

Abstract

The Galactic magnetic field (GMF) plays a role in many astrophysical processes and is a significant foreground to cosmological signals, such as the Epoch of Reionization (EoR), but is not yet well understood. Dispersion and Faraday rotation measurements (DMs and RMs, respectively) towards a large number of pulsars provide an efficient method to probe the three-dimensional structure of the GMF. Low-frequency polarisation observations with large fractional bandwidth can be used to measure precise DMs and RMs. This is demonstrated by a catalogue of RMs (corrected for ionospheric Faraday rotation) from the Low Frequency Array (LOFAR), with a growing complementary catalogue in the southern hemisphere from the Murchison Widefield Array (MWA). These data further our knowledge of the three-dimensional GMF, particularly towards the Galactic halo. Recently constructed or upgraded pathfinder and precursor telescopes, such as LOFAR and the MWA, have reinvigorated low-frequency science and represent progress towards the construction of the Square Kilometre Array (SKA), which will make significant advancements in studies of astrophysical magnetic fields in the future. A key science driver for the SKA-Low is to study the EoR, for which pulsar and polarisation data can provide valuable insights in terms of Galactic foreground conditions.