Evidence for a Gradual Decline in the Universal Rest-Frame Ultraviolet Luminosity Density for [CLC][ITAL]z[/ITAL][/CLC] < 1

Abstract

We have utilized various magnitude-limited samples drawn from an extremely deep and highly complete spectroscopic redshift survey of galaxies observed in seven colors in the Hawaii Survey Fields and the Hubble Deep Field to investigate the evolution of the universal rest-frame ultraviolet luminosity density from z = 1 to the present. The multicolor data (U', B, V, R, and I, J, HK') enable the sample selection to be made in the rest-frame ultraviolet for the entire redshift range. Because of the large sample size and depth (U_AB = 24.75, B_AB = 24.75, I_AB = 23.5), we are able to accurately determine the luminosity density to z = 1. We do not confirm the very steep evolution reported by Lilly et al. but instead find a shallower slope, approximately (1 + z)^1.5 for q₀ = 0.5, which would imply that galaxy formation is continuing smoothly to the present time rather than peaking at z = 1. Much of the present formation is taking place in smaller galaxies. Detailed comparisons with other recent determinations of the evolution are presented.