Modelling self-interacting dark matter substructures I: Calibration with N-body simulations of a Milky-Way-sized halo and its satellite

Abstract

We study evolution of single subhaloes with their masses of $\sim 10^9{M}_{\odot }$ in a Milky-Way-sized host halo for self-interacting dark matter (SIDM) models. We perform dark-matter-only N-body simulations of dynamical evolution of individual subhaloes orbiting its host by varying self-scattering cross sections (including a velocity-dependent scenario), subhalo orbits, and internal properties of the subhalo. We calibrate a gravothermal fluid model to predict time evolution in spherical mass density profiles of isolated SIDM haloes with the simulations. We find that tidal effects of SIDM subhaloes can be described with a framework developed for the case of collision-less cold dark matter (CDM), but a shorter typical time scale for the mass loss due to tidal stripping is required to explain our SIDM simulation results. As long as the cross section is less than $\sim 10{\mathrm{cm}}^2/\mathrm{g}$ and initial states of subhaloes are set within a $2\sigma$-level scatter at redshifts of $\sim 2$ predicted by the standard $\Lambda$CDM cosmology, our simulations do not exhibit a prominent feature of gravothermal collapse in the subhalo central density for 10 Gyr. We develop a semi-analytic model of SIDM subhaloes in a time-evolving density core of the host with tidal stripping and self-scattering ram pressure effects. Our semi-analytic approach provides a simple, efficient and physically-intuitive prediction of SIDM subhaloes, but further improvements are needed to account for baryonic effects in the host and the gravothermal instability accelerated by tidal stripping effects.

19 pages, 12 figures, 1 table. Accepted for publication in MNRAS. Note that results in the previous manuscript (v1) were affected by a bug in our SIDM implementation. We fixed the bug and updated all results accordingly

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• Testing the parametric model for self-interacting dark matter using matched halos in cosmological simulations
• SASHIMI-SIDM: Semi-analytical subhalo modelling for self-interacting dark matter at sub-galactic scales
• Constraining the Nature of Dark Matter from Tidal Radii of Cluster Galaxy Subhalos