Ultra-faint dwarf galaxies (UFDs) are the oldest, the least luminous and the most metal-poor galaxies ever known, and they are predicted to be the first star forming systems hosting the first (Pop III) stars. In this talk, I will show that UFDs are the perfect systems to study the early chemical enrichment and the properties of Pop III stars, such as their Initial Mass Function (IMF) and the explosion energy of the first supernovae (SNe). To this end, I will present a novel theoretical model that follows the formation and chemical evolution of Boötes I, the best studied UFD galaxy, by accounting for the incomplete sampling of the IMF and by investigating the chemical enrichment by different sources. I’ll prove that Pop III SNe leave key chemical signatures in their descendants, which can be uniquely identify through their A(C) values. Then, I’ll show that Pop III enriched stars can be found among both Carbon-Enhanced and C-normal metal-poor stars, also showing that two stars in Boötes I have a chemical abundance pattern respectively consistent with a 100% enrichment by faint, and 84% enrichment by hypernovae. Finally I will demonstrate that UFDs, due to their shallow potential well mainly retain the chemical products of low-energy Pop III SNe and thus the probability to find the imprint of PISN is extremely low in these systems.
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