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

TL;DR

This study compares two simulation codes, Gizmo and Arepo, in modeling self-interacting dark matter (SIDM) effects on halo evolution, finding consistent results within 30% during core expansion phases across different implementations.

Contribution

It provides a systematic comparison of SIDM implementations in Gizmo and Arepo, demonstrating their robustness and reliability in predicting core formation in dark matter halos.

Findings

Codes agree within 30% on density profiles during core expansion

Varying SIDM parameters affects central density by less than 10% outside convergence radius

Both codes reliably differentiate between SIDM cross-sections of 1, 5, and 50 cm^2 g^{-1}

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 $\rm cm^2 g^{-1}$. 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 $\rm cm^2 g^{-1}$ but finer distinctions would require further investigation.