Dark matter halo concentrations in the Wilkinson Microwave Anisotropy Probe year 5 cosmology

TL;DR

This study investigates how dark matter halo concentrations depend on mass and redshift within the WMAP5 cosmology, revealing lower concentrations than some previous models and observations, with implications for understanding cosmic structure formation.

Contribution

It provides a detailed analysis of halo concentration-mass relations using N-body simulations tailored to WMAP5 parameters, contrasting with earlier higher sigma_8 models.

Findings

Halo concentration follows a power-law with mass for z<2.

WMAP5-based concentrations are 16-23% lower than Millennium Simulation.

Predicted concentrations are lower than those inferred from X-ray observations.

Abstract

We use a combination of three large N-body simulations to investigate the dependence of dark matter halo concentrations on halo mass and redshift in the WMAP year 5 cosmology. The median relation between concentration and mass is adequately described by a power-law for halo masses in the range 10^11 - 10^15 Msol/h and redshifts z < 2, regardless of whether the halo density profiles are fit using NFW or Einasto profiles. Compared with recent analyses of the Millennium Simulation, which uses a value of sigma_8 that is higher than allowed by WMAP5, z = 0 halo concentrations are reduced by factors ranging from 23 per cent at 10^11 Msol/h to 16 per cent at 10^14 Msol/h. The predicted concentrations are much lower than inferred from X-ray observations of groups and clusters.