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 un iverse provides a powerful test for the geometry of the universe. Usin g reasonable galaxy evolution models of population synthesis that repr oduce the colors of local galaxies of various morphological types, we have calculated the luminosity density of galaxies as a function of re dshift z. Comparison of the result with recent measurements by the Can ada-France Redshift Survey in three wave bands of 2800 Angstrom, 4400 Angstrom and 1 mu m at z < 1 indicates that the Lambda-dominated flat universe with lambda(0) similar to 0.8 is favored, and the lower limit on lambda(0) yields 0.37 (99% C.L.) or 0.53 (95% C.L.) if Omega(0) lambda(0) = 1. The Einstein-de Sitter universe with (Omega(0), lambda( 0)) = (1, 0) and the low-density open universe with (0.2, 0) are, howe ver, ruled out with 99.86% C.L. and 98.6% C.L., respectively. The conf idence levels quoted apply unless the standard assumptions on galaxy e volution are drastically violated.We have also calculated a global sta r formation rate in the universe to be compared with the observed rate beyond z similar to 2. We find from this comparison that spiral galax ies are formed from material accreted over an extended period of a few Gyr, while elliptical galaxies are formed from an initial starburst a t z greater than or similar to 5 that supplies enough metals and ioniz ing photons in the intergalactic medium.