Virial scaling of massive dark matter halos: Why clusters prefer a high normalization cosmology

A. E. Evrard, J. Bialek, M. Busha, M. White, S. Habib, K. Heitmann, M. Warren, E. Rasia, G. Tormen, L. Moscardini, C. Power, A. R. Jenkins, L. Gao, C. S. Frenk, V. Springel, S. D.M. White, J. Diemand

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299 Citations (Scopus)


We present a precise estimate of the bulk virial scaling relation of halos formed via hierarchical clustering in an ensemble of simulated cold dark matter cosmologies. The result is insensitive to cosmological parameters; the presence of a trace, dissipationless gas component; and numerical resolution down to a limit of ∼ 1000 particles. The dark matter velocity dispersion scales with total mass as log[σDM(M, z)] = log(1082.9 ± 4.0 km s_1) + (0.3361 ± 0.0026)log [h(z)M200 /10 15 M], with h(z) being the dimensionless Hubble parameter. At fixed mass, the velocity dispersion likelihood is nearly lognormal, with scatter σln σ = 0.0426 ± 0.015, except for a tail with higher dispersions containing 10% of the population that are merger transients. We combine this relation with the halo mass function in ACDM models and show that a low normalization condition, S8 = σ8m/0.3)0.35 = 0.69, favored by recent WMAP and SDSS analysis requires that galaxy and gas-specific energies in rich clusters be 50% larger than that of the underlying dark matter. Such large energetic biases are in conflict with the current generation of direct simulations of cluster formation. A higher normalization, S8 = 0.80, alleviates this tension and implies that the hot gas fraction within r 500 is (0.71 ± 0.09) h70-3/2 Ωbm, a value consistent with recent Sunyaev-Zel'dovich observations.

Original languageEnglish
Pages (from-to)122-137
Number of pages16
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 1 Jan 2008
Externally publishedYes


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