The cosmology dependence of the concentration-mass-redshift relation

Abstract

The concentrations of dark matter haloes provide crucial information about their internal structure and how it depends on mass and redshift -the so-called concentration-mass-redshift relation, denoted 𝑐(𝑀, 𝑧). We present here an extensive study of the cosmology-dependence of 𝑐(𝑀, 𝑧) that is based on a suite of 72 gravity-only, full N-body simulations in which the following cosmological parameters were varied: 𝜎 8 , Ω M , Ω b , 𝑛 s , ℎ, 𝑀 𝜈 , 𝑤 0 and 𝑤 a . We characterize the impact of these parameters on concentrations for different halo masses and redshifts. In agreement with previous works, and for all cosmologies studied, we find that there exists a tight correlation between the characteristic densities of dark matter haloes within their scale radii, 𝑟 −2 , and the critical density of the Universe at a suitably defined formation time. This finding, when combined with excursion set modelling of halo formation histories, allows us to accurately predict the concentrations of dark matter haloes as a function of mass, redshift, and cosmology. We use our simulations to test the reliability of a number of published models for predicting halo concentration and highlight when they succeed or fail to reproduce the cosmological 𝑐(𝑀, 𝑧) relation.