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Magnetic Fields and Halos in Spiral Galaxies

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Galaxies 2019, 7(2), 54; https://doi.org/10.3390/galaxies7020054
Received: 18 February 2019 / Revised: 14 April 2019 / Accepted: 18 April 2019 / Published: 4 May 2019
(This article belongs to the Special Issue New Perspectives on Galactic Magnetism)
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Abstract

Radio continuum and polarization observations reveal best the magnetic field structure and strength in nearby spiral galaxies. They show a similar magnetic field pattern, which is of spiral shape along the disk plane and X-shaped in the halo, sometimes accompanied by strong vertical fields above and below the central region of the disk. The strength of the total halo field is comparable to that of the disk. The small- and large-scale dynamo action is discussed to explain the observations with special emphasis on the rôle of star formation on the α - Ω dynamo and the magnetic field strength and structure in the disk and halo. Recently, with RM-synthesis of the CHANG-ES observations, we obtained the first observational evidence for the existence of regular magnetic fields in the halo. The analysis of the radio scale heights indicate escape-dominated radio halos with convective cosmic ray propagation for many galaxies. These galactic winds may be essential for an effective dynamo action and may transport large-scale magnetic field from the disk into the halo.
Keywords: galaxies: spiral; galaxies: magnetic fields; galaxies: halos; galaxies: star formation; galaxies: galactic winds; galaxies: evolution; radio continuum: galaxies galaxies: spiral; galaxies: magnetic fields; galaxies: halos; galaxies: star formation; galaxies: galactic winds; galaxies: evolution; radio continuum: galaxies
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Krause, M. Magnetic Fields and Halos in Spiral Galaxies. Galaxies 2019, 7, 54.

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