The mass–concentration–redshift relation of cold and warm dark matter haloes

• Published in: Monthly notices of the Royal Astronomical Society Vol. 460; no. 2; pp. 1214 - 1232
• Main Authors: Ludlow, Aaron D., Bose, Sownak, Angulo, Raúl E., Wang, Lan, Hellwing, Wojciech A., Navarro, Julio F., Cole, Shaun, Frenk, Carlos S.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01-08-2016
• Subjects: Approximation; Assembly; Astronomy; Computer simulation; Cosmology; Dark matter; Halos; Red shift; Self-similarity; Simulation; methods: numerical; dark matter; galaxies: haloes
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw1046

We use a suite of cosmological simulations to study the mass–concentration–redshift relation, c(M, z), of dark matter haloes. Our simulations include standard Λ-cold dark matter (CDM) models, and additional runs with truncated power spectra, consistent with a thermal warm dark matter (WDM) scenario. We find that the mass profiles of CDM and WDM haloes are self-similar and well approximated by the Einasto profile. The c(M, z) relation of CDM haloes is monotonic: concentrations decrease with increasing virial mass at fixed redshift, and decrease with increasing redshift at fixed mass. The mass accretion histories (MAHs) of CDM haloes are also scale-free, and can be used to infer concentrations directly. These results do not apply to WDM haloes: their MAHs are not scale-free because of the characteristic scale imposed by the power spectrum suppression. Further, the WDM c(M, z) relation is non-monotonic: concentrations peak at a mass scale dictated by the truncation scale, and decrease at higher and lower masses. We show that the assembly history of a halo can still be used to infer its concentration, provided that the total mass of its progenitors is considered (the ‘collapsed mass history’; CMH), rather than just that of its main ancestor. This exploits the scale-free nature of CMHs to derive a simple scaling that reproduces the mass–concentration–redshift relation of both CDM and WDM haloes over a vast range of halo masses and redshifts. Our model therefore provides a robust account of the mass, redshift, cosmology and power spectrum dependence of dark matter halo concentrations.