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arXiv · 2510.05258

Self-interacting dark matter in the center of a Local Group dwarf galaxy and its satellites

Thales A. Gutcke·Giulia Despali·Stephanie O'Neil·Mark Vogelsberger·Azadeh Fattahi·David B. Sanders
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Abstract

We present a detailed comparison of a Local Group dwarf galaxy analogue evolved in two cosmological models: the standard $\Lambda$CDM and a self-interacting dark matter (SIDM) model with a velocity-dependent cross-section. Both simulations are run with the high-resolution, hydrodynamical LYRA galaxy formation model, allowing us to explore the global and substructure properties of the dwarf in a consistent context. While the overall halo growth, final mass, and subhalo mass functions remain largely unchanged across models, SIDM produces a central dark matter core extending to $\sim$1 kpc, which does not significantly vary with the inclusion of baryons. Baryonic properties, however, differ notably. The SIDM model leads to a 25% reduction in stellar mass and retains more gas within the stellar half-mass radius due to a prolonged quiescent phase in star formation. The stellar distribution is less centrally concentrated, and a population of in-situ star clusters form at late times. Substructure analysis reveals fewer luminous satellites and more stellar-only systems in SIDM, driven in part by tidal stripping that affects the dark matter more than the stars. A subset of satellites undergoes tidal-triggered core collapse after infall, enhancing the diversity of SIDM satellite rotation curves. These differences offer potential observational signatures of SIDM in low-mass galaxies.

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Thales A. Gutcke, Giulia Despali, Stephanie O'Neil, Mark Vogelsberger, Azadeh Fattahi, David B. Sanders. 2025-10-06. Self-interacting dark matter in the center of a Local Group dwarf galaxy and its satellites. https://arxiv.org/abs/2510.05258

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