The Thousand-Pulsar-Array programme on MeerKAT – XVI. Mapping the Galactic magnetic field with pulsar observations
The Thousand-Pulsar-Array programme on MeerKAT – XVI. Mapping the Galactic magnetic field with pulsar observations
Measuring the magnetic field of the Milky Way reveals the structure and evolution of the Galaxy. Pulsar rotation measures (RMs) provide a means to probe this Galactic magnetic field (GMF) in three dimensions. We use the largest single-origin data set of pulsar measurements, from the MeerKAT Thousand-Pulsar-Array, to map out GMF components parallel to pulsar lines of sight. We also present these measurements for easy integration into the consolidated RM catalogue, RMTable. Focusing on the Galactic disc, we investigate competing theories of how the GMF relates to the spiral arms, comparing our observational map with five analytic models of magnetic field structure. We also analyse RMs to extragalactic radio sources, to help build-up a three-dimensional picture of the magnetic structure of the Galaxy. In particular, our large number of measurements allows us to investigate differing magnetic field behaviour in the upper and lower halves of the Galactic plane. We find that the GMF is best explained as following the spiral arms in a roughly bisymmetric structure, with antisymmetric parity with respect to the Galactic plane. This picture is complicated by variations in parity on different spiral arms, and the parity change location appears to be shifted by a distance of 0.15 kpc perpendicular to the Galactic plane. This indicates a complex relationship between the large-scale distributions of matter and magnetic fields in our Galaxy. Future pulsar discoveries will help reveal the origins of this relationship with greater precision, as well as probing the locations of local magnetic field inhomogenities.
Galaxy: disc, ISM: magnetic fields, magnetic fields, pulsars: general
2112-2130
Oswald, L.S.
37bd35fc-2e68-4a79-8ada-fefaa61fa959
Weltevrede, P.
cf899f41-558f-4425-8685-3defdab81444
Posselt, B.
5a1e6250-c7d1-4d91-b049-bc4d6d95c090
Johnston, S.
6f6f0f59-44fd-456f-80d6-5c3e258a4226
Karastergiou, A.
73474642-e322-4d91-a886-b822c385d07b
Lower, M.E.
8f5f4753-cf05-4c4a-a6f5-aff809874f64
6 June 2025
Oswald, L.S.
37bd35fc-2e68-4a79-8ada-fefaa61fa959
Weltevrede, P.
cf899f41-558f-4425-8685-3defdab81444
Posselt, B.
5a1e6250-c7d1-4d91-b049-bc4d6d95c090
Johnston, S.
6f6f0f59-44fd-456f-80d6-5c3e258a4226
Karastergiou, A.
73474642-e322-4d91-a886-b822c385d07b
Lower, M.E.
8f5f4753-cf05-4c4a-a6f5-aff809874f64
Oswald, L.S., Weltevrede, P., Posselt, B., Johnston, S., Karastergiou, A. and Lower, M.E.
(2025)
The Thousand-Pulsar-Array programme on MeerKAT – XVI. Mapping the Galactic magnetic field with pulsar observations.
Monthly Notices Of The Royal Astronomical Society, 540 (3), .
(doi:10.1093/mnras/staf645).
Abstract
Measuring the magnetic field of the Milky Way reveals the structure and evolution of the Galaxy. Pulsar rotation measures (RMs) provide a means to probe this Galactic magnetic field (GMF) in three dimensions. We use the largest single-origin data set of pulsar measurements, from the MeerKAT Thousand-Pulsar-Array, to map out GMF components parallel to pulsar lines of sight. We also present these measurements for easy integration into the consolidated RM catalogue, RMTable. Focusing on the Galactic disc, we investigate competing theories of how the GMF relates to the spiral arms, comparing our observational map with five analytic models of magnetic field structure. We also analyse RMs to extragalactic radio sources, to help build-up a three-dimensional picture of the magnetic structure of the Galaxy. In particular, our large number of measurements allows us to investigate differing magnetic field behaviour in the upper and lower halves of the Galactic plane. We find that the GMF is best explained as following the spiral arms in a roughly bisymmetric structure, with antisymmetric parity with respect to the Galactic plane. This picture is complicated by variations in parity on different spiral arms, and the parity change location appears to be shifted by a distance of 0.15 kpc perpendicular to the Galactic plane. This indicates a complex relationship between the large-scale distributions of matter and magnetic fields in our Galaxy. Future pulsar discoveries will help reveal the origins of this relationship with greater precision, as well as probing the locations of local magnetic field inhomogenities.
Text
2504.09722v2
- Author's Original
Text
staf645
- Version of Record
More information
Accepted/In Press date: 31 March 2025
e-pub ahead of print date: 24 April 2025
Published date: 6 June 2025
Keywords:
Galaxy: disc, ISM: magnetic fields, magnetic fields, pulsars: general
Identifiers
Local EPrints ID: 502824
URI: http://eprints.soton.ac.uk/id/eprint/502824
ISSN: 1365-2966
PURE UUID: ef54edb2-f923-4f1f-a762-d83920bca61e
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Date deposited: 09 Jul 2025 16:30
Last modified: 14 Aug 2025 02:11
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Contributors
Author:
L.S. Oswald
Author:
P. Weltevrede
Author:
B. Posselt
Author:
S. Johnston
Author:
A. Karastergiou
Author:
M.E. Lower
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