Abondance des éléments plus légers que le zinc dans les premières étoiles galactiques - Implications sur la nature des premières supernovæ

摘要

During my Ph. D. I have analyzed $33$ extremely metal-deficient galactic halo stars (stars having less than $500$ times less metals than the Sun) observed at the VLT, using the high resolution spectrograph UVES. These stars are relics from the very first ages of our Galaxy, and thus provide useful constraints on both the formation and on the evolution models of our Galaxy.I determined the abundances for $17$ elements from carbon to zinc with an unprecedented accuracy, including the key elements oxygen and zinc, tounderstand which kind of supernova had enriched the interstellar medium during the early times of the Galaxy.I have shown in this work that we could explain the observed abundance ratio witout including very massive supernova (stars whose mass is greater then $100$Msol).In addition, the abundance trends are compared with Galactic chemical evolution models. As the study is based on very metal poor stars that are supposed to be born during the first ages of our Galaxy, my work brings strong new observational constraints to these models.