Evidence For a Gradual Decline in the Universal
Rest-Frame Uv Luminosity Density for z < 1
Lennox L. Cowie, Antoinette Songaila & Amy J. Barger
(Astronomical Journal, in press, August 1999)
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 multi-color data (U', B, V, R, I, J, HK') enable the sample
selection to be made in the rest-frame ultraviolet for the entire
redshift range. Due to 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. (1996) 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.
Antoinette Songaila Cowie
(acowie@uhifa.ifa.hawaii.edu)
Last Revision : February, 1998