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A subgrid turbulent mean field dynamo model for cosmological galaxy formation simulations

Liu, Yuankang; Kretschmer, Michael; Teyssier, Romain

A subgrid turbulent mean field dynamo model for cosmological galaxy formation simulations Thumbnail


Michael Kretschmer

Romain Teyssier


Magnetic fields have been included in cosmological simulations of galaxy formation only recently. In this paper, we develop a new subgrid model for the turbulent dynamo that takes place in the supersonic interstellar medium in star-forming galaxies. It is based on a mean-field approach that computes the turbulent kinetic energy at unresolved scales and modifies the induction equation to account for the corresponding α dynamo. Our subgrid model depends on one free parameter, the quenching parameter, that controls the saturation of the subgrid dynamo. Thanks to this mean-field approach, we can now model the fast amplification of the magnetic field inside turbulent star-forming galaxies without using prohibitively expensive high-resolution simulations. We show that the evolution of the magnetic field in our zoom-in Milky Way-like galaxy is consistent with a simple picture, in which the field is in equipartition with the turbulent kinetic energy inside the star-forming disc, with a field strength around 10 μG at low redshift, while at the same time strong galactic outflows fill the halo with a slightly weaker magnetic field, whose strength (10 nG) is consistent with the ideal magnetohydrodynamic dilution factor. Our results are in good agreement with recent theoretical and numerical predictions. We also compare our simulation with Faraday depth observations at both low and high redshifts, seeing overall good agreement with some caveats. Our model naturally predicts stronger magnetic fields at high redshift (around 100 μG in the galaxy and 1 μG in the halo), but also stronger depolarization effects due to stronger turbulence at early time.


Liu, Y., Kretschmer, M., & Teyssier, R. (2022). A subgrid turbulent mean field dynamo model for cosmological galaxy formation simulations. Monthly Notices of the Royal Astronomical Society, 513(4), 6028-6041.

Journal Article Type Article
Acceptance Date Apr 14, 2022
Online Publication Date May 11, 2022
Publication Date 2022-07
Deposit Date Jul 14, 2022
Publicly Available Date Jul 14, 2022
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 513
Issue 4
Pages 6028-6041


Published Journal Article (3.2 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2022 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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