The Nature of Lyman-Break Galaxies

The number density and clustering properties of Lyman-break galaxies(LBGs)observed at redshift z～3 are best explained by assuming that they are associated with the most massive haloes at z～3 predicted in hierarchical models of structure fo rmation.In this paper we study, under the same assumption, how star formation and chemical enrichment may have proceeded in the LBG population.We find that gas cooling in dark haloes provides a natural regulation process. The predicted star formation rates and effective radii are consistent with observations.Still, the predicted metallicity distribution, the contribution to the total metals and the contributions to the soft X-ray background and to the UV ionization backg round of LBGs are presented and the discussions are given.