The first (Pop III) stars produce the very first metals and inject them in the pristine Universe through supernova (SN) explosions. The chemical traces of Pop III SNe can be searched for in different environments and through cosmic times: e.g. in the Galactic halo, which hosts the most metal-poor stars ever observed, and in distant absorption systems. In this talk I will present a general parametric model for early metal enrichment that allows us to study the chemical abundances (from C to Zn) of environments imprinted by a single Pop III SN. We investigate how these abundances depend on the initial mass and SN explosion energy of Pop III stars and how subsequent generations of normal (Pop II) SNe affect their chemical signatures. By comparing the C, O, Mg, Si and Fe abundances of halo stars with our model predictions, we find that stars with [C/Fe]≥+2.5 likely form in environments only polluted by a single low-energy Pop III SN and exhibit a large chemical dispersion among them. Conversely, as normal Pop II SNe contribute to the enrichment of the gas, the chemical dispersion among the Pop III star descendants formed in this medium, decreases. I will use this prediction to show that most C-normal stars ([C/Fe]≤+0.7) are likely enriched by Pop II SNe at ≥50% level. Finally, I will show that our general model can be used to interpret the newly discovered high-z absorption systems and present novel diagnostics to pinpoint the signature of the Pop III SNe in distant gas clouds.
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