Sensitivity of halo shape measurements

Fischer, M.; Valenzuela, Lucas M.

doi:10.1051/0004-6361/202245031

Cited by 3 publications

(3 citation statements)

References 53 publications

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“…We show it only for the collisionless DM and the strongest fSIDM model of each velocity-dependence. In addition, we indicate at which radius the shape sensitivity (Fischer & Valenzuela 2023) for the 25th percentile drops below a value of 25. This is indicative of a radius above which the shape measurements are reliable.…”

Section: Shapesmentioning

confidence: 83%

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Cosmological simulations with rare and frequent dark matter self-interactions

Fischer

Brüggen

Schmidt-Hoberg

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Dark matter (DM) with self-interactions is a promising solution for the small-scale problems of the standard cosmological model. Here we perform the first cosmological simulation of frequent DM self-interactions, corresponding to small-angle DM scatterings. The focus of our analysis lies in finding and understanding differences to the traditionally assumed rare DM (large-angle) self scatterings. For this purpose, we compute the distribution of DM densities, the matter power spectrum, the two-point correlation function and the halo and subhalo mass functions. Furthermore, we investigate the density profiles of the DM haloes and their shapes. We find that overall large-angle and small-angle scatterings behave fairly similarly with a few exceptions. In particular, the number of satellites is considerably suppressed for frequent compared to rare self-interactions with the same cross-section. Overall we observe that while differences between the two cases may be difficult to establish using a single measure, the degeneracy may be broken through a combination of multiple ones. For instance, the combination of satellite counts with halo density or shape profiles could allow discriminating between rare and frequent self-interactions. As a by-product of our analysis, we provide - for the first time - upper limits on the cross-section for frequent self-interactions.

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Section: Shapesmentioning

confidence: 83%

“…of the haloes cannot be measured accurately. The vanishing density gradient within the density core of SIDM haloes renders the shape undefined (Fischer & Valenzuela 2023).…”

Section: Shapesmentioning

confidence: 99%

Cosmological simulations with rare and frequent dark matter self-interactions

Fischer

Brüggen

Schmidt-Hoberg

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…We consider the shape fit to be converged when the difference between axial ratios vary by less than 10 −4 between iterations. Fischer & Valenzuela ( 2023 ) show that the halo shape cannot be reliably determined within a flat density core. Ho we ver, since none of the simulations analysed here are completely cored, this does not affect our analysis.…”

Section: Shape Algorithmmentioning

confidence: 91%

EDGE: the shape of dark matter haloes in the faintest galaxies

Orkney,

Taylor,

Read

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Collisionless dark matter only (DMO) structure formation simulations predict that dark matter (DM) haloes are prolate in their centres and triaxial towards their outskirts. The addition of gas condensation transforms the central DM shape to be rounder and more oblate. It is not clear, however, whether such shape transformations occur in ‘ultra-faint’ dwarfs, which have extremely low baryon fractions. We present the first study of the shape and velocity anisotropy of ultra-faint dwarf galaxies that have gas mass fractions of fgas(r < Rhalf) < 0.06. These dwarfs are drawn from the Engineering Dwarfs at Galaxy formation’s Edge (EDGE) project, using high-resolution simulations that allow us to resolve DM halo shapes within the half-light radius (∼100 pc). We show that gas-poor ultra-faints (M200c ≤ 1.5 × 109 M⊙; fgas < 10−5) retain their pristine prolate DM halo shape even when gas, star formation, and feedback are included. This could provide a new and robust test of DM models. By contrast, gas-rich ultra-faints (M200c > 3 × 109 M⊙; fgas > 10−4) become rounder and more oblate within ∼10 half-light radii. Finally, we find that most of our simulated dwarfs have significant radial velocity anisotropy that rises to $\tilde{\beta } \gt 0.5$ at R ≳ 3Rhalf. The one exception is a dwarf that forms a rotating gas/stellar disc because of a planar, major merger. Such strong anisotropy should be taken into account when building mass models of gas-poor ultra-faints.

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Cosmological and idealized simulations of dark matter haloes with velocity-dependent, rare and frequent self-interactions

Fischer,

Kasselmann,

Brüggen

et al. 2024

Monthly Notices of the Royal Astronomical Society

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Dark matter self-interactions may have the capability to solve or at least mitigate small-scale problems of the cosmological standard model, ΛCDM. There are a variety of self-interacting dark matter (SIDM) models that lead to distinguishable astrophysical predictions and hence varying success in explaining observations. Studies of dark matter (DM) density cores on various mass scales suggest a velocity-dependent scattering cross-section. In this work we investigate how a velocity dependence alters the evolution of the DM distribution for frequent DM scatterings and compare to the velocity-independent case. We demonstrate that these cases are qualitatively different using a test problem. Moreover, we study the evolution of the density profile of idealised DM haloes and find that a velocity dependence can lead to larger core sizes and different time scales of core formation and core collapse. In cosmological simulations, we investigate the effect of velocity-dependent self-interaction on haloes and satellites in the mass range of ≈1011–1014 M⊙. We study the abundance of satellites, density and shape profiles and try to infer qualitative differences between velocity-dependent and velocity-independent scatterings as well as between frequent and rare self-interactions. We find that a strongly velocity-dependent cross-section can significantly amplify the diversity of rotation curves, independent of the angular dependence of the differential cross-section. We further find that the abundance of satellites in general depends on both the velocity dependence and the scattering angle, although the latter is less important for strongly velocity-dependent cross-sections.

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Sensitivity of halo shape measurements

Cited by 3 publications

References 53 publications

Cosmological simulations with rare and frequent dark matter self-interactions

Cosmological simulations with rare and frequent dark matter self-interactions

EDGE: the shape of dark matter haloes in the faintest galaxies

Cosmological and idealized simulations of dark matter haloes with velocity-dependent, rare and frequent self-interactions

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