The most massive distant clusters: Determining Ω and σ8

Neta A. Bahcall, Xiaohui Fan

Research output: Contribution to journalArticlepeer-review

302 Scopus citations


The existence of the three most massive clusters of galaxies observed so far at z > 0.5 is used to constrain the mass density parameter of the universe, Ω, and the amplitude of mass fluctuations, σ8. We find Ω = 0.2-0.1+0.3 and σ8 = 1.2-0.4+0.5 (95%). We show that the existence of even the single most distant cluster at z = 0.83, MS 1054-03, with its large gravitational lensing mass, high temperature, and large velocity dispersion, is sufficient to establish powerful constraints. High-density, Ω = 1 (σ8 ≃ 0.5-0.6) Gaussian models are ruled out by these data (10-6 probability); the Ω = 1 models predict only 10-5 massive clusters at z > 0.65 (∼10-3 at z > 0.5) instead of the one (three) clusters observed.

Original languageEnglish (US)
Pages (from-to)1-6
Number of pages6
JournalAstrophysical Journal
Issue number1 PART I
StatePublished - 1998

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: observations
  • Cosmology: theory
  • Galaxies: clusters: general
  • Galaxies: evolution
  • Large-scale structure of universe


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