{
  "id": "astro-ph/0510643",
  "version": "v1",
  "published": "2005-10-21T14:45:35.000Z",
  "updated": "2005-10-21T14:45:35.000Z",
  "title": "Galaxy Groups in the 2dFGRS: the number density of groups",
  "authors": [
    "V. R. Eke",
    "C. M. Baugh",
    "S. Cole",
    "C. S. Frenk",
    "J. F. Navarro"
  ],
  "comment": "Submitted to MNRAS, 12 pages, 17 figures (1 in colour)",
  "journal": "Mon.Not.Roy.Astron.Soc.370:1147-1158,2006",
  "doi": "10.1111/j.1365-2966.2006.10568.x",
  "categories": [
    "astro-ph"
  ],
  "abstract": "The abundance of galaxy clusters as a function of mass is determined using the 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue. This is used to estimate the amplitude of the matter fluctuation spectrum, parametrised by the linear theory rms density fluctuations in spheres of 8Mpc/h, sigma_8. The best-fitting value for this parameter is highly correlated with the mean matter density in the Universe, Omega_m, and is found to satisfy sigma_8=0.25Omega_m^{-0.92-4.5(Omega_m-0.22)^2}+/-10%(statistical)+/-20% (systematic) for 0.18<Omega_m<0.50, assuming that Omega_m+Omega_Lambda=1. This gives sigma_8=0.89 when Omega_m=0.25. A ~20% correction has been applied to undo the systematic bias inherent in the measurement procedure. Mock catalogues, constructed from large cosmological N-body simulations, are used to help understand and model these systematic errors. The abundance of galaxy groups as a function of group bj band luminosity is also determined. This is used in conjunction with the halo mass function, determined from simulations, to infer the variation of halo mass-to-light ratio over four orders of magnitude in halo mass. The mass-to-light ratio shows a minimum value of 100hM_sol/L_sol in the bj band at a total group luminosity of L_bJ ~ 5.10^9Lsol/h^2. Together with the observed Tully-Fisher relation, this implies that the observed rotation speed of Tully-Fisher galaxies is within ~10% of the typical circular speed of haloes hosting brightest galaxies of the same luminosity.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2005-10-21T14:45:35.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "number density",
      "linear theory rms density fluctuations",
      "group bj band luminosity",
      "total group luminosity",
      "haloes hosting brightest galaxies"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "Wiley-Blackwell",
      "journal": "J. Finance"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 695825
    }
  }
}