The Evolution of Dust Opacity in Galaxies

Abstract

We investigate the evolution of the opacity of galaxies as a function of redshift, using simple assumptions about the metal and dust enrichment of the gas and the distribution of dust in galaxies. The method presented in this paper uses an iterative procedure to reconstruct the intrinsic star formation rate (SFR) density of galaxies as a function of redshift, by correcting the observed UV emission for the obscuring effects of the dust produced by the star formation itself. Where necessary, gas inflows/outflows are included to dilute/remove the excess of metals produced by the stars for fixed yield. The iterative procedure converges to multiple solutions for the intrinsic SFR density, divided into two basic classes. The first class of solutions predicts a relatively large amount of UV attenuation at high redshift, with A1500 ? = 1.9 mag at z ~ 3, and smaller attenuations at low redshift (z < 1), with A2800 ? = 1.25 mag. The SFR density of this set of solutions is constant for z 1.2 and declines for z < 1.2; it resembles in shape the monolithic collapse scenario for star formation. The second class of solutions predicts relatively low-UV attenuations at high redshift, with A1500 ? = 0.75 mag at z ~ 3, and larger attenuations at low redshift, with A2800 ? = 1.50 mag at z < 1. The SFR density in this case has a peak at z 1.2. The advantages and shortcomings of both classes are analyzed in the light of available observational constraints, including the opacity of galaxies at 0 ? z ? 1 and the intensity and spectral energy distribution of the cosmic infrared background from the COBE DIRBE and FIRAS data. We conclude that both classes of models are acceptable within the current uncertainties, but the monolithic collapse class matches the available observations better than the other one. We also investigate the dependence of our solutions on the different model assumptions.