A measurement of the mass density of the universe

This letter reports a new measurement of the density parameter Ω, which is the mass density of the universe relative to the critical density. The authors have measured the redshifts and fluxes of 1,000 field galaxies with a median redshift of 0.5. With this sample they determine Ω by measuring the volume element (to a scale factor H₀³) as a function of redshift. The measurement is sensitive to any kind of matter, luminous or dark. It is found that Ω = 0.9 (+0.7, -0.5), consistent with the Einstein-de Sitter model (Λ = 0, Ω = 1).