MARVELously Dark: the density profile evolution of dwarf halos in velocity-dependent SIDM

Abstract Self-interacting dark matter (SIDM) with a sufficiently large cross section has been shown to naturally produce constant dark matter (DM) cores, as well as core-collapse, at the centers of dwarf halos on cosmic timescales, potentially reducing tensions with observation. Here, we present halos from a new dark matter only (DMO) cosmological (SIDM) simulation: Ms.Marvel DMO with a velocity-dependent self-interaction cross section with σ / m max = 50 cm 2 /g at v max = 35 km/s. We compare these to the CDM suite of Storm simulations including both DMO and dark matter + hydrodynamics runs, in order to test core-formation (and core-collapse) across different dark matter models. We show that Ms.Marvel DMO can reproduce core slopes consistent with observations of isolated dwarf galaxies and more massive (M vir ≳ 10 10 M ⊙ ) CDM dwarf halos that include stellar feedback from the matched CDM run (Storm CDM+baryons). We identify nine Ms.Marvel SIDM DMO halos in the core-collapse phase of gravothermal evolution with halo masses below 2 × 10 9 M ⊙ . We find that using the inner density slope to measure the core-collapse timescales of Ms.Marvel DMO halos agrees well with predicted collapse times estimated with the parametric model for SIDM halos introduced by [1]. Additionally, compared to central density, the inner density slope is less sensitive to both the radius of measurement and halo merger history. These results indicate that the slope of the inner DM density profile more cleanly differentiates core-collapsed versus core-forming halos than central density amplitude.