The First Generation of Stars: First Steps toward Chemical Evolution of Galaxies

We argue that extreme metal-poor stars show a high dispersion in metallicity, because their abundances are the outcome of very few supernova events. Abundance anomalies should appear because of the discrete range of progenitor masses. There is a natural metallicity threshold of Z / Z ☉ ~ 10 -4 below which one would expect to find very few, if any, halo stars. Similar reasoning is applied to lower mass systems, such as metal-poor compact blue galaxies and Lyman-alpha absorption-line clouds seen toward high-redshift quasars, where a somewhat higher threshold is inferred.