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

Evrard, A.E. and Bialek, J. and Busha, M. and White, M. and Habib, S. and Heitmann, K. and Warren, M. and Rasia, E. and Tormen, G. and Moscardini, L. and Power, C. and Jenkins, A.R. and Gao, L. and Frenk, C.S. and Springel, V. and White, S.D.M. and Diemand, J. (2008) 'Virial scaling of massive dark matter halos : why clusters prefer a high normalization cosmology.', Astrophysical journal., 672 (1). pp. 122-137.

Abstract

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 log½ ¼ DM(M;z) log (1082:9 4:0 km s1) þ (0:3361 0:0026)log h(z)M200 /10 ½ 15 M , with h(z) being the dimensionless Hubble parameter. At fixed mass, the velocity dispersion likelihood is nearly lognormal, with scatter ln ¼ 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 CDM models and show that a low normalization condition, S8 ¼ 8(m /0:3)0:35 ¼ 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 ¼ 0:80, alleviates this tension and implies that the hot gas fraction within r500 is (0:71 0:09) h3=2 70 b /m, a value consistent with recent Sunyaev-Zel’dovich observations.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1086/521616
Publisher statement:© 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A.
Record Created:20 Apr 2016 10:50
Last Modified:21 Feb 2017 17:49

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