The halo mass dependence of physical and observable properties in the circumgalactic medium at z = 0

Cook, Andrew W. S., van de Voort, Freeke ORCID: https://orcid.org/0000-0002-6301-638X, Pakmor, Rüdiger and Grand, Robert J. J. 2025. The halo mass dependence of physical and observable properties in the circumgalactic medium at z = 0. Monthly Notices of the Royal Astronomical Society 543 (2) , pp. 1224-1238. 10.1093/mnras/staf1537

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Abstract

We study the dependence of the physical and observable properties of the circumgalactic medium on its halo mass in 25 high resolution cosmological ‘zoom-in’ simulations from the Auriga suite. We focus on the current epoch (z = 0) and on halo masses of M⊙ and stellar masses of 107 M⊙ ≤ M⋆ ≤ 1011 M⊙. The mass resolution of our simulations is 5.4 × 103 M⊙. This work analyses the temperature, density, metallicity and radial velocity of these haloes and the column density of H i, Mg ii, Si ii, C iv and O vi. We find median temperature and metallicity increase with halo mass as expected. We find a larger scatter in temperature at higher halo masses, suggesting that the multiphase nature of the CGM is halo mass dependent. Our H i column densities show good agreement with observations at all radii. Mg ii and Si ii match observations between 0.1R200c-0.3R200c, but decrease steeply with radius. O vi column densities are underpredicted by our simulations for stellar masses between 109.5 M⊙ ≤ M⋆ < 1010.2 M⊙ at large radii with reasonable agreement at 1011 M⊙. C iv column densities agree with observational detections above a halo mass of 109.5M⊙. We find that O vi (H i) traces the highest (lowest) temperatures, and lowest (highest) density and metallicity. O vi (C iv) is photo-ionized (collisionally ionized) at low (high) halo masses with a transition to higher temperatures at 1011 M⊙. Our results demonstrate similarities and discrepancies between simulations of Milky Way-mass haloes and observations. They also show further observational constraints are needed in less massive haloes.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2025-09-13
Publisher:	Oxford University Press
ISSN:	0035-8711
Date of First Compliant Deposit:	29 October 2025
Date of Acceptance:	9 September 2025
Last Modified:	29 Oct 2025 10:53
URI:	https://orca.cardiff.ac.uk/id/eprint/181395

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