Spectrum and Origin of the Extragalactic Optical Background Radiation

Abstract

Ultra-deep CCD surveys to 29 mag from .32 to .9 μ wavelength reveal an isotropic population of very blue galaxies. There are over 150,000 of these objects per square degree per magnitude. Saturation of their number density at 27 mag indicates that most of the optical light from this population has been detected. The resulting extragalactic background radiation from the UV to the near-IR due to this population of objects is shown. Gravitational lens and Lyman-break observations show that the redshift of galaxies fainter than 24 mag is in the range 1–3. Small-scale dark lane structures may be intergalactic dust clouds or tunnels through the luminous galaxy distribution.