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

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

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.

Citation

Evrard, A., Bialek, J., Busha, M., White, M., Habib, S., Heitmann, K., …Diemand, J. (2008). Virial Scaling of Massive Dark Matter Halos: Why Clusters Prefer a High Normalization Cosmology. Astrophysical Journal, 672(1), 122-137. https://doi.org/10.1086/521616

• Journal Article Type: Article
• Publication Date: Jan 1, 2008
• Deposit Date: Feb 27, 2012
• Publicly Available Date: Apr 20, 2016
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 672
• Issue: 1
• Pages: 122-137
• DOI: https://doi.org/10.1086/521616