Cosmic emissivity and background intensity from damped lyman-alpha galaxies

. Our method is based entirely on data from quasar absorption-line studies, namely, the comoving density of HI and the mean metallicity and dust-to-gas ratio in damped Ly

\alpha

galaxies. These observations, when combined with models of cosmic chemical evolution, are sufficient to determine the comoving rate of star formation as a function of redshift. From this, we compute \E_\nu and

J_\nu

using stellar population synthesis models. Our method includes a self-consistent treatment of the absorption and reradiation of starlight by dust. In all of our calculations, the near-UV emissivity declines rapidly between

z\approx1

and

z=0

, in agreement with estimates from the Canada-France Redshift Survey. The background intensity is consistent with a wide variety of observational limits and with a tentative detection at far-IR wavelengths.

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