Dark Matter Halo Profiles of Massive Clusters: Theory vs. Observations

Details Dark Matter Halo Profiles of Massive Clusters: Theory vs. Observations Dark Matter Halo Profiles of Massive Clusters: Theory vs. Observations

2011-12-22

arxiv.org/abs/1112.5479v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

17 pages; 12 figures

Scientific paper

We study dark matter halo profiles using a suite of numerical simulations. We carry out (gravity-only) simulations of the current concordance LCDM cosmology, covering a halo mass range of 2.10^(12) to 2.10^(15) solar masses and a redshift range of z=0-2, dictated primarily by cluster observation considerations. We find that the shape of the concentration-mass (c-M) relation flattens at high redshift and this flattening of the slope is naturally expressed if c is written as a function of the peak height parameter, \nu. Although the logarithmic slope of the c-M relation changes with redshift, that of the (c-\nu) relation is effectively constant over the redshift range z=0-2. The amplitude of c(\nu) varies by about 30% from z=0-2 over the mass range for massive clusters. The (c-\nu) relation is, however, not universal. We use a large suite of simulations covering the currently allowed wCDM parameter space and show that the (c-\nu) relation varies by about +/- 20 % when cosmological parameters are varied. We find that the distribution of the concentrations can be well-fit by a Gaussian with variance, \sigma_c=0.33c, where the ratio of the variance to the mean, \sigma_c/c, is independent of the radius at which the concentration is defined, the dynamical state of the halo, and the underlying cosmology. We compare our simulation predictions with current results obtained from (primarily low) redshift observations and find good agreement with the observational data for massive clusters of mass > 4.10^(14) solar masses, but there are disagreements at lower masses. Because of uncertainty in observational systematics and modeling of baryonic physics, the significance of these discrepancies remains to be understood. (Abridged)

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