Dark matter halo shapes in the Auriga simulations

Prada, J.; Forero-Romero, Jaime E.; Grand, Robert J. J.; Pakmor, Rüdiger; Springel, Volker

doi:10.1093/mnras/stz2873

Cited by 54 publications

(53 citation statements)

References 49 publications

(71 reference statements)

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“…The inner regions of the halo are only slightly flattened, with b/a ∼ 0.95 and c/a ∼ 0.85, and the axial ratios show very little variation with radius; we can therefore make robust predictions for the shape of the inner DM halo. We note that the inner haloes in simulations that include baryons are typically rounder than in DM-only simulations (Bailin et al 2005;Velliscig et al 2015a;Chua et al 2019;Prada et al 2019), with the dominant effect being the potential of the baryons, which is very important for r/R 200 ≤ 0.2. At larger distances, the haloes become systematically more flattened and, at the same time, show greater halo-to-halo variation.…”

Section: The Structure Of the Dm Halomentioning

confidence: 80%

The twisted dark matter halo of the Milky Way

Shao

Cautun

Deason

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We analyse systems analogous to the Milky Way (MW) in the eagle cosmological hydrodynamics simulation in order to deduce the likely structure of the MW’s dark matter halo. We identify MW-mass haloes in the simulation whose satellite galaxies have similar kinematics and spatial distribution to those of the bright satellites of the MW, specifically systems in which the majority of the satellites (8 out of 11) have nearly co-planar orbits that are also perpendicular to the central stellar disc. We find that the normal to the common orbital plane of the co-planar satellites is well aligned with the minor axis of the host dark matter halo, with a median misalignment angle of only 17.3○. Based on this result, we infer that the minor axis of the Galactic dark matter halo points towards (l, b) = (182○, −2○), with an angular uncertainty at the 68 and 95 percentile confidence levels of 22○ and 43○ respectively. Thus, the inferred minor axis of the MW halo lies in the plane of the stellar disc. The halo, however, is not homologous and its flattening and orientation vary with radius. The inner parts of the halo are rounder than the outer parts and well aligned with the stellar disc (that is the minor axis of the halo is perpendicular to the disc). Further out, the halo twists and the minor axis changes direction by 90○. This twist occurs over a very narrow radial range and reflects variations in the filamentary network along which mass was accreted into the MW.

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Section: The Structure Of the Dm Halomentioning

confidence: 80%

The twisted dark matter halo of the Milky Way

Shao

Cautun

Deason

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…They reported a median misalignment angle of about 33°between the central galaxy and the DM halo. Prada et al (2019) studied the radial profile of the alignment between the DM halo and the stellar disk in a sample of 30 MW-like galaxies from the Auriga simulation and found a very high level of alignment between these vectors in most galaxies in their sample and at various radii. Additionally, they reported a significant change in the alignment in some cases, implying some level of twists.…”

Section: Comparison Between the Shape Of The Dm And The Sdmentioning

confidence: 99%

Inferring the Morphology of Stellar Distribution in TNG50: Twisted and Twisted-stretched Shapes

Emami

Hernquist

Alcock

et al. 2021

ApJ

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We investigate the morphology of the stellar distribution (SD) in a sample of Milky Way-like galaxies in the TNG50 simulation. Using a local in shell iterative method as the main approach, we explicitly show evidence of twisting (in about 52% of halos) and stretching (in 48% of them) in real space. This is matched with the reorientation observed in the eigenvectors of the inertia tensor and gives us a clear picture of having a reoriented SD. We make a comparison between the shape profile of the dark matter (DM) halo and SD and quite remarkably see that their radial profiles are fairly close, especially at small galactocentric radii, where the stellar disk is located. This implies that the DM halo is somewhat aligned with stars in response to the baryonic potential. The level of alignment mostly decreases away from the center. We study the impact of substructures in the orbital circularity parameter. It is demonstrated that in some cases, faraway substructures are counterrotating compared with the central stars and may flip the sign of total angular momentum and thus the orbital circularity parameter. Truncating them above 150 kpc, however, retains the disky structure of the galaxy as per initial selection. Including the impact of substructures in the shape of stars, we explicitly show that their contribution is subdominant. Overlaying our theoretical results on the observational constraints from previous literature, we establish fair agreement.

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“…An additional possibility one may consider is that these structures arise from orbits of stars moving in a dark matter halo that significantly departs from spherical symmetry due to past mergers with dwarf galaxies. However, it is likely that such an effect is minimal close to the midplane as prior work studying the evolution of halo shapes finds that baryonic-dominated regions are nearly spherical (Debattista et al 2008;Prada et al 2019).…”

Section: Birth Heightsmentioning

confidence: 99%

Birth Sites of Young Stellar Associations and Recent Star Formation in a Flocculent Corrugated Disk

Quillen,

Pettitt,

Chakrabarti

et al. 2020

Preprint

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With backwards orbit integration we estimate birth locations of young stellar associations and moving groups identified in the solar neighborhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun's Galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a corrugated disk of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighborhood. This would be expected if they were born in a spiral arm which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low velocity dispersion disk stars.

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Dark matter halo shapes in the Auriga simulations

Cited by 54 publications

References 49 publications

The twisted dark matter halo of the Milky Way

The twisted dark matter halo of the Milky Way

Inferring the Morphology of Stellar Distribution in TNG50: Twisted and Twisted-stretched Shapes

Birth Sites of Young Stellar Associations and Recent Star Formation in a Flocculent Corrugated Disk

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