Found 3 talks width keyword Population III
Extremely metal-poor or zero-metallicity very massive stars, with initial mass in the range 100 ≲ Mi/M⊙ ≲ 1000, have a broad astrophysical impact. Understanding how these population III stars evolve and die has implications for several key questions, including the nature of energetic transients such as pair-instability supernovæ and gamma-ray bursts, the source of extreme ionizing UV-radiation fields at high redshifts, the earliest chemical enrichment of their host galaxies and the rates of gravitational-wave emission from merging black holes among others. There are not many models in literature that follow the evolution of these population III stars, and even less so that reach the phases where the production of electron-positron pairs alter the stability of the whole star. We present new evolutionary models of very massive primordial stars, with initial masses ranging from 100 M☉ to 1000 M☉, that extend from the main sequence until the onset of dynamical instability. We focus on the final outcome of the models and associated compact remnants. Stars that avoid the pair-instability supernova channel, should produce black holes with masses ranging from ~ 40 M☉ to ~ 1000 M☉. In particular, stars with initial masses of about 100 M☉ could leave black holes of ≃ 85-90 M☉, values consistent with the estimated primary black hole mass of the GW190521 merger event. Overall, these results may contribute to explain future data from next-generation gravitational-wave detectors, such as the Einstein Telescope and Cosmic Explorer, which will have access to as-yet unexplored BH mass range of ~ 10^2-10^4 M☉ in the early universe.
To understand the early phases of galaxy formation, metal-poor stars in the local universe play a special rôle, allowing to trace both how galactic assembly proceeds, and the conditions in which early star formation proceed. Metal-poor stars in our Galaxy and its satellites are fossils of these past processes and have therefore been the subject of intense dedicated searches and surveys since decades. Here I shall review some of the recent results that the « Pristine » narrow-band photometric survey at CFHT, has enabled, aided by the transformational information brought by the Gaia space mission. These results range from enravelling a very primordial disc in the Milky-Way, characterizing very pristine streams of stars in the galactic halo, and characterizing the co-existing halo and bulge populations in the inner parts of the Milky-Way. Finally, I will outline the plans to characterise further these extreme and very metal-poor stars with the new WEAVE multi-object facility that should start its science surveys early 2023.
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