## Abstract

Using sensitive centimeter-wave receivers mounted on the Owens Valley Radio Observatory and Berkeley-Illinois-Maryland-Association millimeter arrays, we have obtained interferometric measurements of the Sunyaev-Zeldovich (SZ) effect toward massive galaxy clusters. We use the SZ data to determine the pressure distribution of the cluster gas and, in combination with published X-ray temperatures, to infer the gas mass and total gravitational mass of 18 clusters. The gas mass fraction, f_{g}, is calculated for each cluster and is extrapolated to the fiducial radius r_{500} using the results of numerical simulations. The mean f_{g} within r_{500} is 0.081 ^{+0.009}_{-0.011} h^{-1}_{100} (statistical uncertainty at 68% confidence level, assuming Ω_{M} = 0.3, Ω_{Λ} = 0.7). We discuss possible sources of systematic errors in the mean f_{g} measurement. We derive an upper limit for Ω_{M} from this sample under the assumption that the mass composition of clusters within r_{500} reflects the universal mass composition: Ω_{M} h ≤ Ω_{B}/f_{g}. The gas mass fractions depend on cosmology through the angular diameter distance and the r_{500} correction factors. For a flat universe (Ω_{Λ} = 1 - Ω_{M}) and h = 0.7, we find the measured gas mass fractions are consistent with Ω_{M} < 0.40, at 68% confidence. Including estimates of the baryons contained in galaxies and the baryons which failed to become bound during the cluster formation process, we find Ω_{M} ∼ 0.25.

Original language | English (US) |
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Pages (from-to) | 2-14 |

Number of pages | 13 |

Journal | Astrophysical Journal |

Volume | 552 |

Issue number | 1 PART 1 |

DOIs | |

State | Published - May 1 2001 |

Externally published | Yes |

## Keywords

- Cosmic microwave background
- Cosmology: observations
- Galaxies: clusters: general
- Techniques: interferometric

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science

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