Dottorato - PhD thesis
Area Tematica: RSN 1 - Galassie e Cosmologia
Referenti: Gabriella De Lucia (
Titolo: Metal enrichment in the early Universe
Decorrenza: 09.06.2024
Descrizione:
The first stars that illuminated our Universe also synthesized the first chemical elements heavier than Helium (called metals). These were then released into the surrounding gas through stellar winds and supernova (SN) explosions. Entrapped in the outflows, metals were potentially able to reach outside the galaxy virial radius into the diffuse gas named circum- and inter-galactic medium (CGM and IGM, respectively). The chemically enriched gas surrounding galaxies was discovered observationally through the absorption signatures left in the spectra of background bright quasars, and the cross-correlation between absorptions and galaxies in the same field. Large observational samples of absorption lines are now available over almost the entire life of the Universe, out to z~7, at less than 1 billion years from the Big Bang. However, the potential amount of information that could be derived from these data has not yet been fully exploited due to the dearth of theoretical models providing predictions to be compared with the observations. Modeling early metal enrichment requires treating several scales simultaneously, from the interstellar medium where star formation takes place, to the larger scales of the CGM and IGM, and accounting for several processes that can transfer mass and metals from stars/galaxies to the surrounding medium (e.g. feedback from stars and active galactic nuclei). Recent work based on hydrodynamical simulations was unable to reproduce statistical properties of observed absorption lines, likely because of the small simulated volumes. In this project, we will build on a state-of-the-art semi-analytic model (the Galaxy Evolution and Assembly model) coupled to high-resolution dark matter N-body simulation, and develop analytic/semi-analytic prescriptions to trace the chemical enrichment of gas around simulated galaxies. The model includes a sophisticated treatment of chemical enrichment that accounts for the non-instantaneous recycling of gas and metals, and reproduces the observed galaxy mass-metallicity relation up to high-redshift. The large volume accessible through this technique will allow building mock spectra that we will compare with observed metal absorption lines, thereby placing strong constraints on the circulation of metals (and baryons in general) within and outside galactic haloes. The advantage of the semi-analytic technique will be the possibility to test different enrichment scenarios, varying e.g. the size of the enriched regions or the loading factors of energy and metals. The framework adopted will offer the unique possibility to use observations of metals both within and outside galaxies to constrain the physical processes considered.
