Constraining Ω with cluster evolution

Neta A. Bahcall, Xiaohui Fan, Renyue Cen

Research output: Contribution to journalArticle

190 Citations (Scopus)

Abstract

We show that the evolution of the number density of rich clusters of galaxies breaks the degeneracy between Ω (the mass density ratio of the universe) and σ8 (the normalization of the power spectrum), σ8Ω0.5 ≃ 0.5, that follows from the observed present-day abundance of rich clusters. The evolution of high-mass (Coma-like) clusters is strong in Ω = 1, low-σ8 models (such as the standard biased cold dark matter model with σ8 ≃ 0.5), where the number density of clusters decreases by a factor of about 103 from z = 0 to z ≃ 0.5; the same clusters show only mild evolution in low-Ω, high-σ8 models, where the decrease is a factor of about 10. This diagnostic provides a most powerful constraint on Ω. Using observations of clusters to z ≃ 0.5-1, we find only mild evolution in the observed cluster abundance. We find Ω = 0.3 ± 0.1 and σ8 = 0.85 ± 0.15 (for A = 0 models; for Ω + Λ = 1 models, Ω = 0.34 ± 0.13). These results imply, if confirmed by future surveys, that we live in a low-density, low-bias universe.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume485
Issue number2 PART II
StatePublished - 1997
Externally publishedYes

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universe
coma
power spectra
dark matter
galaxies
normalisation
cold

Keywords

  • Cosmology: observations
  • Cosmology: theory
  • Dark matter
  • Galaxies: clusters: general
  • Galaxies: evolution
  • Galaxies: formation

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Bahcall, N. A., Fan, X., & Cen, R. (1997). Constraining Ω with cluster evolution. Astrophysical Journal, 485(2 PART II).

Constraining Ω with cluster evolution. / Bahcall, Neta A.; Fan, Xiaohui; Cen, Renyue.

In: Astrophysical Journal, Vol. 485, No. 2 PART II, 1997.

Research output: Contribution to journalArticle

Bahcall, NA, Fan, X & Cen, R 1997, 'Constraining Ω with cluster evolution', Astrophysical Journal, vol. 485, no. 2 PART II.
Bahcall, Neta A. ; Fan, Xiaohui ; Cen, Renyue. / Constraining Ω with cluster evolution. In: Astrophysical Journal. 1997 ; Vol. 485, No. 2 PART II.
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AB - We show that the evolution of the number density of rich clusters of galaxies breaks the degeneracy between Ω (the mass density ratio of the universe) and σ8 (the normalization of the power spectrum), σ8Ω0.5 ≃ 0.5, that follows from the observed present-day abundance of rich clusters. The evolution of high-mass (Coma-like) clusters is strong in Ω = 1, low-σ8 models (such as the standard biased cold dark matter model with σ8 ≃ 0.5), where the number density of clusters decreases by a factor of about 103 from z = 0 to z ≃ 0.5; the same clusters show only mild evolution in low-Ω, high-σ8 models, where the decrease is a factor of about 10. This diagnostic provides a most powerful constraint on Ω. Using observations of clusters to z ≃ 0.5-1, we find only mild evolution in the observed cluster abundance. We find Ω = 0.3 ± 0.1 and σ8 = 0.85 ± 0.15 (for A = 0 models; for Ω + Λ = 1 models, Ω = 0.34 ± 0.13). These results imply, if confirmed by future surveys, that we live in a low-density, low-bias universe.

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KW - Dark matter

KW - Galaxies: clusters: general

KW - Galaxies: evolution

KW - Galaxies: formation

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