Dark matter haloes in the multicomponent model – I. Substructure

Multicomponent dark matter with self-interactions, which allows for interconversions of species, is a promising paradigm that is known to successfully and simultaneously resolve major problems of the conventional lambda cold dark matter (ΛCDM) cosmology at galactic and subgalactic scales. In this paper, we present N-body simulations of the simplest two-component (2cDM) model aimed at studying the distribution of dark matter haloes with masses $M\lesssim 10^{12}\, \mathrm{M}_\odot$. In particular, we investigate how the maximum circular velocity function of the haloes is affected by the velocity dependence of the self-interaction cross-sections, σ(v) ∝ v^a, and compare it with available observational data. The results demonstrate that the 2cDM paradigm with the range of self-interaction cross-section per particle mass (evaluated at v = 100 km s⁻¹) of 0.01 ≲ σ0/m ≲ 1 cm² g⁻¹ and the mass degeneracy Δm/m ∼ 10⁻⁷–10⁻⁸ robustly resolves the substructure and too-big-to-fail problems by suppressing the substructure having small maximum circular velocities, Vmax ≲ 100 km s⁻¹. We also discuss the disagreement between the radial distribution of dwarfs in a host halo observed in the Local Group and simulated with CDM. This can be considered as one more small-scale problem of CDM. We demonstrate that such a disagreement is alleviated in 2cDM. Finally, the computed matter power spectra of the 2cDM structure indicate the model's consistency with the existing Ly α forest constraints.