Gravothermal collapse and the diversity of galactic rotation curves

Abstract

The rotation curves of spiral galaxies exhibit a great diversity that challenge our understanding of galaxy formation and the nature of dark matter. Previous studies showed that in self-interacting dark matter (SIDM) models with a cross section per unit mass of $\sigma /m\approx \mathcal{O}(1)\mathrm{c}{\mathrm{m}}^2/g$, the predicted dark matter central densities are a good match to the observed densities in galaxies. In this work, we explore a regime with a larger cross section of $\sigma /m\approx 20\text{-}40\mathrm{c}{\mathrm{m}}^2/g$ in dwarf galactic halos. We will show that such strong dark matter self-interactions can further amplify the diversity of halo densities inherited from their assembly history. High concentration halos can enter the gravothermal collapse phase within $10\mathrm{Gyr}$, resulting in a high density, while low concentration ones remain in the expansion phase and have a low density. We fit the rotation curves of $14$ representative low surface brightness galaxies and demonstrate how the large range of observed central densities are naturally accommodated in the strong SIDM regime of $\sigma /m\approx 20\text{-}40\mathrm{c}{\mathrm{m}}^2/g$. Galaxies that are outliers in the previous studies due to their high halo central densities, are no longer outliers in this SIDM regime as their halos would be in the collapse phase. For galaxies with a low density, the SIDM fits are robust to the variation of the cross section. Our findings open up a new window for testing gravothermal collapse, the unique signature of strong dark matter self-interactions, and exploring a broader SIDM model space. As an example, we illustrate how the larger cross sections favored by our fits, together with upper limits from strong lensing observations in clusters, pick out the preferred SIDM model space for a dark matter particle coupled to a light gauge boson in the Born regime.

23 pages, 14 figures. Accepted for publication in Phys. Rev. D. This version adds a new section discussing the implications of our fits for the SIDM particle physics parameter space

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Cited by in corpus (10)

• Formation of the Little Red Dots from the Core-collapse of Self-interacting Dark Matter Halos
• SIDM Concerto: Compilation and Data Release of Self-interacting Dark Matter Zoom-in Simulations
• Testing CCC+TL Cosmology with Galaxy Rotation Curves
• Central densities of dark matter halos in FIRE-2 simulations of low-mass galaxies with cold dark matter and self-interacting dark matter
• Self-Interacting Dark-Matter Spikes and the Final-Parsec Problem: Bayesian constraints from the NANOGrav 15-Year Gravitational-Wave Background
• Constraints on dark matter models from the stellar cores observed in ultra-faint dwarf galaxies: Self-interacting dark matter
• Calibrating the SIDM Gravothermal Catastrophe with N-body Simulations
• Structure Formation with Dark Magnetohydrodynamics
• Neutron Portal and Dark Matter-Baryon Coincidence: from UV Completion to Phenomenology
• Broken Expectations: The Effects of Modelling Assumptions on the Inferred Dark Matter Distribution in the Milky Way's Satellites