Evolution of the Luminosity Density in the Universe: Implications for the Nonzero Cosmological Constant

We show that evolution of the luminosity density of galaxies in the universe provides a powerful test for the geometry of the universe. Using reasonable galaxy evolution models of population synthesis which reproduce the colors of local galaxies of various morphological types, we have calculated the luminosity density of galaxies as a function of redshift z. Comparison of the result with recent measurements by the Canada-France Redshift Survey in three wavebands of 2800Å, 4400Å, and 1μm at z < 1 indicates that the Λ-dominated flat universe with λ0 ∼ 0.8 is favored, and the lower limit on λ0 yields 0.37 (99% C.L.) or 0.53 (95% C.L.) if Ω0 + λ0 = 1. The Einstein-de Sitter universe with (Ω0, λ0) = (1, 0) and the low-density open universe with (0.2, 0) are however ruled out with 99.86% C.L. and 98.6% C.L., respectively. The confidence levels quoted apply unless the standard assumptions on galaxy evolution are drastically violated. We have also calculated a global star formation rate in the universe to be compared with the observed rate beyond z ∼ 2. We find from this comparison that spiral galaxies are formed from material accretion over an extended period of a few Gyrs, while elliptical galaxies are formed from initial star burst at z ∼ 5 supplying enough amount of metals and ionizing photons in the intergalactic medium. Subject headings: galaxies: evolution — galaxies: formation — galaxies: intergalactic medium — cosmology: theory Department of Physics, School of Science, the University of Tokyo, Tokyo 113, Japan E-mail: [email protected] Institute of Astronomy, Faculty of Science, the University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181, Japan Research Center for the Early Universe, School of Science, the University of Tokyo, Tokyo 113, Japan