Dark matter haloes in the multicomponent model – II. Density profiles of galactic haloes

Abstract

The multicomponent dark matter model with self-scattering and inter-conversions of species into one another is an alternative dark matter paradigm that is capable of resolving the longstanding problems of lambda cold dark matter (CDM) cosmology at small scales. In this paper, we have studied in detail the properties of dark matter haloes with M ∼ 4–5 × 1011 M obtained in N-body cosmological simulations with the simplest two-component (2cDM) model. A large set of velocity-dependent cross-section prescriptions for elastic scattering and mass conversions, σs(v) ∝ vas and σc(v) ∝ vac, has been explored and the results were compared with observational data. The results demonstrate that self-interactions with the cross-section per particle mass evaluated at v = 100 km s−1 being in the range of 0.01 σ0/m 1 cm2 g−1 robustly suppress central cusps, thus resolving the core-cusp problem. The core radii are controlled by the values of σ0/m and the DM cross-section’s velocity-dependent power-law indices (as, ac), but are largely insensitive to the species’ mass degeneracy. These values are in full agreement with those resolving the substructure and too-big-to-fail problems. We have also studied the evolution of haloes in the 2cDM model with cosmic time.