## Abstract

We present multiwavelength observations of the Abell 1995 galaxy cluster. From an analysis of X-ray spectroscopy and imaging data, we derive the electron temperature, cluster core radius, and central electron number density. Using optical spectroscopy of 15 cluster members, we derive an accurate cluster redshift and velocity dispersion. Finally, the interferometric imaging of the Sunyaev-Zeldovich effect toward Abell 1995 at 28.5 GHz provides a measure of the integrated pressure through the cluster. The X-ray and Sunyaev-Zeldovich effect observations are combined to determine the angular diameter distance to the cluster of D_{A} = 1294^{+294 +438}_{-283 -458} Mpc (statistical followed by systematic uncertainty), implying a Hubble constant of H_{0} = 52.2^{+11.4 +18.5}_{-11.9 -17.7} km s^{-1} Mpc^{-1} for Ω_{M} = 0.3 and Ω_{Λ} = 0.7. We find a best-fit H_{0} of 46 km s^{-1} Mpc^{-1} for the Ω_{M} = 1 and Ω_{Λ} = 0 cosmology, and 48 km s^{-1} Mpc^{-1} for Ω_{M} = 0.3 and Ω_{Λ} = 0.0. The X-ray data are also used to derive a total cluster mass of M^{HSE}_{tot}(r_{500}) = 5.18^{+0.62}_{-0.48} × 10^{14} h^{-1} M_{⊙}; the optical velocity dispersion yields an independent and consistent estimate of M^{virial}_{tot}(r_{500}) = 6.35^{+1.51}_{-1.19} × 10^{14} h^{-1} M_{⊙}. Both of the total mass estimates are evaluated at a fiducial radius, r_{500} = 830 h^{-1} kpc, where the overdensity is 500 times the critical density. The total cluster mass is then combined with gas mass measurements to determine a cluster gas mass fraction of f_{g} = 0.056^{+0.010}_{-0.013} h^{-3/2}. In combination with recent baryon density constraints, the measured gas mass fraction yields an upper limit on the mass density parameter of Ω_{M} h^{1/2} ≤ 0.34^{+0.06}_{-0.05}.

Original language | English (US) |
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Pages (from-to) | 37-48 |

Number of pages | 12 |

Journal | Astrophysical Journal |

Volume | 541 |

Issue number | 1 PART 1 |

DOIs | |

State | Published - Sep 20 2000 |

Externally published | Yes |

## Keywords

- Cosmology: observations
- Dark matter
- Distance scale
- Galaxies: clusters: individual (Abell 1995)
- X-rays: general

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science