First stars and ultra-faint dwarf galaxies
Martina Rossi (INAF - OAS)
Tuesday 05/03/2024 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
Ultra-faint dwarf galaxies (UFDs) stand out as 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’ll highlight why UFDs stand as the ideal cosmic laboratories, to study the early chemical enrichment and the elusive properties of Pop III stars, such as their Initial Mass Function (IMF) and the explosion energy of the first supernovae (SNe).Moreover I will demonstrate that UFDs, due to their shallow potential welI 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. To this end, I will present a novel theoretical model that follows the formation and chemical evolution ( from carbon to zinc) 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 ( SNe and AGB stars from both Pop III and subsequent PopII stellar populations) . I’ll prove that Pop III SNe leave key chemical signatures in their descendants, which can be uniquely identify through their A(C) values. Next, I’ll reveal in Boötes I the coexistence of Pop III-enriched stars exist within both Carbon-Enhanced and C-normal metal-poor stars. Among literature data of Boötes I stars with at least 5 abundance ratios measured, we uncover one mono-enriched and two multi enriched Pop III descendants which have the chemical signatures of both low- and high- energy Pop III SNe. Finally I’ll introduce a new method that, tracing the ancestors of the PopIII star descendants, has the potential to probe the entire range of mass and energy of the first SNe.