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Virial Scaling of Massive Dark Matter Halos: Why Clusters Prefer a High Normalization Cosmology

A. E. EvrardDepartment of Physics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109J. BialekDepartment of Physics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109M. BushaDepartment of Physics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109M. WhiteDepartments of Physics and Astronomy, University of California, Berkeley, CA 94720S. HabibLos Alamos National Laboratory, Los Alamos, NM 87545K. HeitmannLos Alamos National Laboratory, Los Alamos, NM 87545M. WarrenLos Alamos National Laboratory, Los Alamos, NM 87545E. RasiaUniversity of BolognaG. TormenDipartimento di Astronomia, Universitá di Padova, vicolo dell’Osservatorio 2, I-35122 Padova, ItalyL. MoscardiniDipartimento di Astronomia, Universitá di Bologna, via Ranzani 1, I-40127 Bologna, ItalyC. PowerCentre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, 3122 Victoria, AustraliaA. R. JenkinsDepartment of Physics, Durham University, South Road, Durham DH1 3LE, UKL. GaoDepartment of Physics, Durham University, South Road, Durham DH1 3LE, UKC. S. FrenkDepartment of Physics, Durham University, South Road, Durham DH1 3LE, UKV. SpringelMax-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85740 Garching, GermanyS. D. M. WhiteMax-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85740 Garching, GermanyJ. DiemandHubble Fellow

2008en

ABI

Annotatsiya

We present a precise estimate of the bulk virial scaling relation of halos formed via hierarchical clustering in\nan ensemble of simulated cold dark matter cosmologies. The result is insensitive to cosmological parameters; the\npresence of a trace, dissipationless gas component; and numerical resolution down to a limit of 1000 particles. The\ndark matter velocity dispersion scales with total mass as log½ ¼ DM(M;z) log (1082:9 4:0 km s1) þ (0:3361\n0:0026)log h(z)M200 /10 ½ 15 M , with h(z) being the dimensionless Hubble parameter. At fixed mass, the velocity dispersion\nlikelihood is nearly lognormal, with scatter ln ¼ 0:0426 0:015, except for a tail with higher dispersions\ncontaining 10% of the population that are merger transients. We combine this relation with the halo mass function in\nCDM models and show that a low normalization condition, S8 ¼ 8(m /0:3)0:35 ¼ 0:69, favored by recent WMAP\nand SDSS analysis requires that galaxy and gas-specific energies in rich clusters be 50% larger than that of the underlying\ndark matter. Such large energetic biases are in conflict with the current generation of direct simulations of cluster\nformation. A higher normalization, S8 ¼ 0:80, alleviates this tension and implies that the hot gas fraction within r500\nis (0:71 0:09) h3=2\n70 b /m, a value consistent with recent Sunyaev-Zel’dovich observations.

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DOI: 10.1086/521616

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