{
  "id": "astro-ph/0609314",
  "version": "v2",
  "published": "2006-09-12T11:37:05.000Z",
  "updated": "2007-03-13T12:00:37.000Z",
  "title": "Revisiting the Baryon Fractions of Galaxy Clusters: A Comparison with WMAP 3-year Results",
  "authors": [
    "Ian G. McCarthy",
    "Richard G. Bower",
    "Michael L. Balogh"
  ],
  "comment": "8 pages, 3 figures, MNRAS accepted",
  "journal": "Mon.Not.Roy.Astron.Soc.377:1457-1463,2007",
  "doi": "10.1111/j.1365-2966.2007.11733.x",
  "categories": [
    "astro-ph"
  ],
  "abstract": "The universal baryonic mass fraction (Omega_b/Omega_m) can be sensitively constrained using X-ray observations of galaxy clusters. In this paper, we compare the baryonic mass fraction inferred from measurements of the cosmic microwave background with the gas mass fractions (f_gas) of a large sample of clusters taken from the recent literature. In systems cooler than 4 keV, f_gas declines as the system temperature decreases. However, in higher temperature systems, f_gas(r500) converges to approx. (0.12 +/- 0.02)(h/0.72)^{-1.5}, where the uncertainty reflects the systematic variations between clusters at r500. This is significantly lower than the maximum-likelihood value of the baryon fraction from the recently released WMAP 3-year results. We investigate possible reasons for this discrepancy, including the effects of radiative cooling and non-gravitational heating, and conclude that the most likely solution is that Omega_m is higher than the best-fit WMAP value (we find Omega_m = 0.36^{+0.11}_{-0.08}), but consistent at the 2-sigma level. Degeneracies within the WMAP data require that sigma_8 must also be greater than the maximum likelihood value for consistency between the data sets.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2007-03-13T12:00:37.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "baryon fraction",
      "galaxy clusters",
      "comparison",
      "universal baryonic mass fraction",
      "maximum likelihood value"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "Wiley-Blackwell",
      "journal": "J. Finance"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 725861
    }
  }
}