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

Abstract

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.

Cold Dark Matter and Self-interacting Dark Matter Interpretations of the Strong Gravitational Lensing Object JWST-ER1

“…We set ρ b (r) to be the Hernquist profile in Equation (1) and ρ cdm (r) to be the contracted CDM profile shown in Figure 2 (solid black), and t age = 3.4 Gyr, corresponding to the redshift z ≈ 2. We also assume a constant cross section, which should be regarded an effective cross section for the halo (Yang & Yu 2022;Yang et al 2023b;Fischer et al 2024;Outmezguine et al 2023;Yang et al 2024). For a given value of σ/m, we solve Equations ( 6) and (7) to find the SIDM density profile.…”

Self-interacting Dark Matter Interpretation of Crater II

“…Thus, a viable SIDM model must have a velocity-dependent cross section, which is strong in dwarf galaxies, while diminishing toward the clusters; see Tulin & Yu (2018) and references therein for the discussion about particle physics realizations of SIDM. Nevertheless, we can use an effective constant cross section for a given halo to accurately characterize its gravothermal evolution (Yang & Yu 2022;Fischer et al 2024;Outmezguine et al 2023;Yang et al 2023b). The constant cross sections we take should be regarded as effective cross sections for the Crater II halo.…”