Dark matter halo shapes in the Auriga simulations

Abstract

We present shape measurements of Milky Way-sized dark matter halos 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 $\lesssim 30$ 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 $20\%$ of halos 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.

MNRAS accepted, 13 pages, 11 figures

References in corpus (12)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time
• The Causes of Halo Shape Changes Induced by Cooling Baryons: Disks Versus Substructures
• Evidence for dark matter in the inner Milky Way
• The shape of the inner Milky Way halo from observations of the Pal 5 and GD-1 stellar streams
• A 22 Degree Tidal Tail for Palomar 5
• Origin of chemically distinct discs in the Auriga cosmological simulations
• The Cosmic Ballet II: Spin alignment of galaxies and haloes with large-scale filaments in the EAGLE simulation
• Cosmic web alignments with the shape, angular momentum and peculiar velocities of dark matter haloes
• Alignments between galaxies, satellite systems and haloes
• Evolution of galactic planes of satellites in the EAGLE simulation
• Dark Matter Response to Galaxy Assembly History

Cited by in corpus (5)

• The Stellar Halo of the Galaxy is Tilted & Doubly Broken
• A Tilted Dark Halo Origin of the Galactic Disk Warp and Flare
• Baryonic effects on the detectability of annihilation radiation from dark matter subhaloes around the Milky Way
• Estimating the Oblateness Of Dark Matter Halos Using Neutral Hydrogen Velocity Dispersion
• Cross Section Calculations in Theories of Self-Interacting Dark Matter