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Magnetic field amplification in cosmological zoom simulations from dwarf galaxies to galaxy groups

Pakmor, Rüdiger, Bieri, Rebekka, van de Voort, Freeke ORCID:, Werhahn, Maria, Fattahi, Azadeh, Guillet, Thomas, Pfrommer, Christoph, Springel, Volker and Talbot, Rosie Y 2024. Magnetic field amplification in cosmological zoom simulations from dwarf galaxies to galaxy groups. Monthly Notices of the Royal Astronomical Society 528 (2) , 2308–2325. 10.1093/mnras/stae112

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Magnetic fields are ubiquitous in the Universe. Recently, cosmological simulations of galaxies have successfully begun to incorporate magnetic fields and their evolution in galaxies and their haloes. However, so far they have mostly focused on Milky Way-like galaxies. Here, we analyse a sample of high-resolution cosmological zoom simulations of disc galaxies in haloes with mass from to ⁠, simulated with the Auriga galaxy formation model. We show that with sufficient numerical resolution the magnetic field amplification and saturation is converged. The magnetic field strength reaches equipartition with turbulent energy density for galaxies in haloes with ⁠. For galaxies in less massive haloes, the magnetic field strength saturates at a fraction of equipartition that decreases with decreasing halo mass. For our lowest mass haloes, the magnetic field saturates significantly below 10 per cent of equipartition. We quantify the resolution we need to obtain converged magnetic field strengths and discuss our resolution requirements also in the context of the IllustrisTNG cosmological box simulations. We show that, at z = 0, rotation-dominated galaxies in our sample exhibit for the most part an ordered large-scale magnetic field, with fewer field reversals in more massive galaxies. Finally, we compare the magnetic fields in our cosmological galaxies at z = 0 with simulations of isolated galaxies in a collapsing halo set-up. Our results pave the way for detailed studies of cosmic rays and other physical processes in similar cosmological galaxy simulations that crucially depend on the strength and structure of magnetic fields.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 26 January 2024
Date of Acceptance: 9 January 2024
Last Modified: 31 Jan 2024 09:45

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