Formation of the Little Red Dots from the Core-collapse of Self-interacting Dark Matter Halos

Abstract

We present a statistical study of black hole (BH) formation and growth seeded by gravothermal core collapse of self-interacting dark matter (SIDM) halos at high redshift, using a cosmological semi-analytical framework based on Monte Carlo merger trees. We demonstrate that gravothermal collapse naturally leads to BH formation in high-concentration halos at a characteristic mass scale set by the SIDM cross section, and occurs predominantly in the early Universe. This mechanism is particularly promising for explaining the abundance of the little red dots (LRDs) -- a population of early, apparently galaxy-less active galactic nuclei hosting supermassive BHs. By incorporating this seeding process with simple models of BH growth and assuming a 100% duty cycle, we reproduce the observed LRD mass function for velocity-dependent cross sections of ${\sigma }_{0m}\sim 30{\mathrm{cm}}^2{\mathrm{g}}^{-1}$ and $\omega \sim 80\mathrm{km}{\mathrm{s}}^{-1}$, which are consistent with independent constraints from local galaxies. While higher values of ${\sigma }_{0m}$ (or $\omega$) would overpredict the low-mass (or high-mass) end of the BH mass function, such deviations could be reconciled by invoking a reduced duty cycle or lower Eddington ratio. Our results suggest that the demographics of high-redshift BHs can serve as a novel and complementary probe of SIDM physics.

Submitted to ApJL. See also a companion study by Shen et al. to be submitted soon (2504.00075), exploring statistics of massive black hole formation in the early Universe with dissipative SIDM

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Cited by in corpus (7)

• Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies
• Black Hole Cold Brew: Fermi Degeneracy Pressure
• Self-Interacting Dark Matter with Mass Segregation: A Unified Explanation of Dwarf Cores and Small-Scale Lenses
• An Enhanced Isothermal Jeans Approach to Constraining Dark Matter Self-Interactions from Galactic Kinematics
• Role of prompt cusps in driving the core collapse of SIDM halos
• The Structure and Evolution of LRDs: Insights from JWST NIRSpec Medium and High Resolution Spectroscopy at $z\sim 4$
• Smoluchowski Coagulation Equation and the Evolution of Primordial Black Hole Clusters