Comparing Implementations of Self-Interacting Dark Matter in the Gizmo and Arepo Codes

Abstract

Self-interacting dark matter (SIDM) models have received great attention over the past decade as solutions to the small-scale puzzles of astrophysics. Though there are different implementations of dark matter (DM) self-interactions in N-body codes of structure formation, there has not been a systematic study to compare the predictions of these different implementations. We investigate the implementation of dark matter self-interactions in two simulation codes: Gizmo and Arepo. We begin with identical initial conditions for an isolated $10^{10}$ M${}_{\odot }$ dark matter halo and investigate the evolution of the density and velocity dispersion profiles in Gizmo and Arepo for SIDM cross-section over mass of 1, 5, and 50 $\mathrm{c}{\mathrm{m}}^2{\mathrm{g}}^{-1}$. Our tests are restricted to the core expansion phase where the core density decreases and core radius increases with time. We find better than 30% agreement between the codes for the density profile in this phase of evolution, with the agreement improving at higher resolution. We find that varying code-specific SIDM parameters changes the central halo density by less than 10% outside of the convergence radius. We argue that SIDM core formation is robust across the two different schemes and conclude that these codes can reliably differentiate between cross-sections of 1, 5, and 50 $\mathrm{c}{\mathrm{m}}^2{\mathrm{g}}^{-1}$ but finer distinctions would require further investigation.

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