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Dark matter halo shapes in the Auriga simulations

Prada, J, Forero-Romero, JE, Grand, RJJ, Pakmor, R and Springel, V (2019) Dark matter halo shapes in the Auriga simulations. Monthly Notices of the Royal Astronomical Society, 490 (4). pp. 4877-4888. ISSN 0035-8711

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We present shape measurements of Milky Way-sized dark matter haloes at redshift z = 0 in a suite of 30 zoom simulations from the Auriga project. We compare the results in full magnetohydrodynamics against dark matter-only simulations and find a strong influence of baryons in making dark matter haloes rounder at all radii compared to their dark matter-only counterparts. At distances ≲30 kpc, rounder dark matter distributions correlate with extended massive stellar discs and low-core gas densities. We measure the alignment between the halo and the disc shapes at different radii and find a high degree of alignment at all radii for most of the galaxies. In some cases, the alignment significantly changes as a function of radius implying that the halo shape twists; this effect correlates with recently formed bulges and is almost absent in the dark matter-only simulations. In a comparison against observational constraints, we find that 20 per cent of haloes in our sample are consistent with observational results derived from the Pal 5 stream that favours an almost spherical shape. Including baryons is a required element to achieve this level of agreement. In contrast, none of the simulations (neither dark matter only nor with baryons) match the constraints derived from the Sagittarius stream that favour an oblate dark matter halo.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press (OUP)
SWORD Depositor: A Symplectic
Date Deposited: 19 Apr 2023 11:57
Last Modified: 19 Apr 2023 11:57
DOI or ID number: 10.1093/mnras/stz2873
URI: https://researchonline.ljmu.ac.uk/id/eprint/19316
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