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

TL;DR

This paper investigates the gravothermal evolution of dwarf halos in velocity-dependent self-interacting dark matter (SIDM) models, demonstrating their ability to reproduce observed core slopes and identify core-collapse phases through simulations.

Contribution

It introduces new cosmological SIDM simulations with velocity-dependent cross sections and compares core formation and collapse across different dark matter models.

Findings

SIDM halos can reproduce observed core slopes in dwarf galaxies.

Nine halos are identified in the core-collapse phase below 2×10^9 M_sun.

Core slope is a more reliable indicator of core-collapse than central density.

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 $\sigma/m_\text{max} = 50$ cm$^2$/g at $v_\text{max} = 35$ 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 ($\text{M}_{vir} \gtrsim 10^{10} M_{\odot}$) 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 $2\times 10^9 M_{\odot}$. We find that using core 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 Yang et al.(2023). Additionally, compared to central density, core 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.