Chemo-spectrophotometric evolution of spiral galaxies - V. Properties of galactic discs at high redshift

We explore the implications for the high-redshift universe of 'state-of-the -art' models for the chemical and spectrophotometric evolution of spiral ga laxies. The models are based on simple 'scaling relations' for discs, obtai ned in the framework of cold dark matter models for galaxy formation, and w ere 'calibrated' so as to reproduce the properties of the Milky Way and of nearby discs (at redshift z similar to 0). In this paper, we compare the pr edictions of our 'hybrid' approach to galaxy evolution to observations at m oderate and high redshift. We find that the models are in fairly good agree ment with observations up to z similar to 1, while some problems appear at higher redshift (provided there is no selection bias in the data); these di screpancies may suggest that galaxy mergers (not considered in this work) p layed a nonnegligible role at z > 1. We also predict the existence of a 'un iversal' correlation between abundance gradients and disc scalelengths, ind ependent of redshift.