Early metal enrichment in high-redshift quasars

摘要

Quasars are powerful systems whose spectrum is rich of metal features that allow us toinvestigate the chemical evolution of galaxies even at very high redshift, close to the reionizationepoch. I review the main observational constraints on the metallicity of quasars host galaxies at highredshift and discuss the implications and issues for models of galaxy evolution in the early universe.