TY - JOUR
T1 - Constraining Ω with cluster evolution
AU - Bahcall, Neta A.
AU - Fan, Xiaohui
AU - Cen, Renyue
N1 - Funding Information:
We thank J. P. Ostriker, J. P. E. Peebles, D. N. Spergel, and M. A. Strauss for helpful discussions. This work is supported by NSF grants AST93-15368 and ASC93-18185, and NASA grant NAG5-2759. X. F. thanks the support from an Advisory Council Scholarship.
PY - 1997
Y1 - 1997
N2 - 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.
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.
KW - Cosmology: observations
KW - Cosmology: theory
KW - Dark matter
KW - Galaxies: clusters: general
KW - Galaxies: evolution
KW - Galaxies: formation
UR - http://www.scopus.com/inward/record.url?scp=0008633250&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0008633250&partnerID=8YFLogxK
U2 - 10.1086/310814
DO - 10.1086/310814
M3 - Article
AN - SCOPUS:0008633250
SN - 0004-637X
VL - 485
SP - L53-L56
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART II
ER -