http://arxiv.org/abs/1601.02624
We use a suite of cosmological simulations to study the mass-concentration-redshift relation, $c({\rm M},z)$, of dark matter halos assembled hierarchically. Our runs include both standard $\Lambda$-cold dark matter (CDM) models, as well as several additional simulations with sharply truncated density fluctuation power spectra, such as those expected in a thermal warm dark matter (WDM) scenario. As in earlier work, we find that the mass profiles of CDM and WDM halos are self-similar and well approximated by the Navarro-Frenk-White (NFW) profile. The $c({\rm M},z)$ relation of CDM halos is monotonic: concentrations decrease with increasing virial mass at fixed redshift, and decrease with increasing redshift at fixed mass. The main-progenitor mass accretion histories (MAHs) of CDM halos are also scale-free, a result that has been used to infer halo concentrations directly from MAHs. These results do not apply to WDM halos: their MAHs are not scale-free because of the characteristic scale imposed by the power-spectrum suppression. Further, the WDM $c({\rm M},z)$ relation is not monotonic: concentrations peak at a halo 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 collapsed progenitors is considered (the “collapsed mass history”; CMH), rather than just that of its main ancestor. This follows the original NFW proposal, and exploits the scale-free nature of CMHs to derive a simple scaling that reproduces the mass-concentration-redshift relation of both CDM and WDM halos in our simulations over a vast range of halo masses and cosmic time. Our model therefore provides a robust account of the mass, redshift, cosmology and power spectrum dependence of the concentrations of dark matter halos assembled hierarchically.
A. Ludlow, S. Bose, R. Angulo, et. al.
Wed, 13 Jan 16
69/81
Comments: 20 pages, 15 figures
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