Far-ultraviolet diffuse background and galaxy counts

We have used galaxy counts obtained at 2000 A down to a magnitude of 18.5 to calculate the ultraviolet integrated light of galaxies. The calculation is based on models developed to interpret the galaxy counts. Because of various sources of uncertainty, the extrapolated values lie in the range 40-130 photons cm −2 s −1 A −1 sr −1 . This extrapolated intensity is comparable to the extragalactic ultraviolet background estimated from direct background measurements, demonstrating that the integrated light of galaxies must be a significant contributor to the extragalactic ultraviolet background