The Coherent Magnetic Field of the Milky Way

We present a suite of models of the coherent magnetic field of the Galaxy based on new divergence-free parametric functions describing the global structure of the field. The model parameters are fit to the latest full-sky Faraday rotation measures (RMs) of extragalactic sources and polarized synchro...

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Veröffentlicht in:The Astrophysical journal Jg. 970; H. 1; S. 95 - 126
Hauptverfasser: Unger, Michael, Farrar, Glennys R.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Philadelphia The American Astronomical Society 01.07.2024
IOP Publishing
Schlagworte:
Anisotropy
Astronomical maps
Astronomical models
Cosmic ray astronomy
Cosmic ray diffusion
Cosmic ray electrons
Cosmic ray showers
Cosmic rays
Differential rotation
Divergence
Electron density
Faraday effect
Galactic rotation
Galaxies
Galaxy magnetic fields
Hemispheres
Interstellar magnetic fields
Magnetic fields
Magnetic properties
Microwave Anisotropy Probe
Milky Way
Milky Way Galaxy physics
Milky Way magnetic fields
Pitch (inclination)
ISSN:0004-637X, 1538-4357
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Zusammenfassung:We present a suite of models of the coherent magnetic field of the Galaxy based on new divergence-free parametric functions describing the global structure of the field. The model parameters are fit to the latest full-sky Faraday rotation measures (RMs) of extragalactic sources and polarized synchrotron intensity (PI) maps from the Wilkinson Microwave Anisotropy Probe and Planck. We employ multiple models for the density of thermal and cosmic-ray electrons in the Galaxy, needed to predict the sky maps of RMs and PI for a given Galactic magnetic field (GMF) model. The robustness of the inferred properties of the GMF is gauged by studying many combinations of parametric field models and electron density models. We determine the pitch angle of the local magnetic field (11° ± 1°), explore the evidence for a grand-design spiral coherent magnetic field (inconclusive), determine the strength of the toroidal and poloidal magnetic halo fields below and above the disk (magnitudes the same for both hemispheres within ≈10%), set constraints on the half-height of the cosmic-ray diffusion volume (≥2.9 kpc), investigate the compatibility of RM- and PI-derived magnetic field strengths (compatible under certain assumptions), and check if the toroidal halo field could be created by the shear of the poloidal halo field due to the differential rotation of the Galaxy (possibly). A set of eight models is identified to help quantify the present uncertainties in the coherent GMF spanning different functional forms, data products, and auxiliary input. We present the corresponding sky maps of rates for axion–photon conversion in the Galaxy and deflections of ultrahigh-energy cosmic rays.
Bibliographie:AAS52801
Interstellar Matter and the Local Universe
ObjectType-Article-1
SourceType-Scholarly Journals-1
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content type line 14
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad4a54