The O II Luminosity Density of the Universe

Abstract

Equivalent widths of [O II] 3727 Å lines are measured in 375 faint galaxy spectra taken as part of the Caltech Faint Galaxy Redshift Survey centered on the Hubble Deep Field. The sensitivity of the survey spectra to the [O II] line is computed as a function of magnitude, color, and redshift. The luminosity function of galaxies in the [O II] line, and the integrated luminosity density of the universe in the [O II] line, are computed as a function of redshift. It is found that the luminosity density in the [O II] line was a factor of ~10 higher at redshifts z ~ 1 than it is at the present day. The simplest interpretation is that the star formation rate density of the universe has declined dramatically since z ~ 1.

Based on observations made at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology and the University of California; at the Palomar Observatory, which is owned and operated by the California Institute of Technology; and with the NASA/ESA Hubble Space Telescope, which is operated by AURA under NASA contract NAS 5-26555.