Speaker: Stefania Salvadori (University of Florence, Italy)
Title: First stars' properties: ultimate constraints from Near-field cosmology
Abstract: The properties of the first stars, such as their mass distribution, are almost completely unknown but they control the injection of energy, photons, and newly created heavy elements into the primordial Universe. In the Local Group, we can indirectly study the properties of the first stars by observing the chemical fingerprints left in their ancient stellar descendants and by interpreting these findings with cosmological models and simulations. In this talk, I will show how the minimum mass, characteristic mass, and shape of the first stars' mass distribution can be constrained by using a global approach, which compares detections and non-detections of first stars' descendants with their predicted frequency in different environments: from the Galactic stellar halo to nearby ultra-faint dwarf galaxies. In particular, I will discuss the recent discovery of a halo star likely imprinted by a very massive primordial Pair Instability Supernova and its enormous implications for the first stars' properties. Finally, I will present new chemical diagnostics to uncover the fingerprints of the first stars in more distant gaseous absorbers, thus connecting Near- and Far-field cosmology.