Convergence Tests and Applications of SIDM Core-Collapse Simulations

Self-interacting dark matter (SIDM) predicts that dark matter halos experience core-collapse, a process where the halo’s inner region rapidly increases in density and decreases in size. Because of the short timescales and high densities involved, N-body simulations of the process are numerically challenging. We perform convergence tests of core-collapsing SIDM halos across a range of halo concentrations and SIDM cross-sections, and quantify potential numerical issues. Due to the extreme nature of core-collapse, a convergence study of this level of detail has not been performed previously. We determine the necessary constraints to avoid these numerical issues and discuss how to diagnose them. Using these newly tested simulations, we probe the physics of SIDM, including calibration of the gravothermal fluid model and possible dark matter constraints from substructure lensing.