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Magnetising the circumgalactic medium of disk galaxies

Pakmor, Rudiger, van de Voort, Freeke ORCID:, Bieri, Rebekka, Gomez, Facundo A., Grand, Robert J. J., Guillet, Thomas, Marinacci, Federico, Pfrommer, Christoph, Simpson, Christine M. and Springel, Volker 2020. Magnetising the circumgalactic medium of disk galaxies. Monthly Notices of the Royal Astronomical Society 498 (3) , pp. 3125-3137. 10.1093/mnras/staa2530

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The circumgalactic medium (CGM) is one of the frontiers of galaxy formation and intimately connected to the galaxy via accretion of gas on to the galaxy and gaseous outflows from the galaxy. Here, we analyse the magnetic field in the CGM of the Milky Way-like galaxies simulated as part of the AURIGA project that constitutes a set of high-resolution cosmological magnetohydrodynamical zoom simulations. We show that before z = 1 the CGM becomes magnetized via galactic outflows that transport magnetized gas from the disc into the halo. At this time, the magnetization of the CGM closely follows its metal enrichment. We then show that at low redshift an in situ turbulent dynamo that operates on a time-scale of Gigayears further amplifies the magnetic field in the CGM and saturates before z = 0. The magnetic field strength reaches a typical value of 0.1μG at the virial radius at z = 0 and becomes mostly uniform within the virial radius. Its Faraday rotation signal is in excellent agreement with recent observations. For most of its evolution, the magnetic field in the CGM is an unordered small-scale field. Only strong coherent outflows at low redshift are able to order the magnetic field in parts of the CGM that are directly displaced by these outflows.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 18 August 2020
Date of Acceptance: 17 August 2020
Last Modified: 11 Nov 2023 03:23

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