Probing the physical and chemical state of the Intergalactic Medium with hydrodynamical simulations

The main goal of my PhD project is to characterize the properties of the intergalactic medium (IGM) around galaxies at high redshift, in order to study the galaxy/intergalactic medium interplay. In fact, intergalactic space provides a critical laboratory to investigate the baryon cycle that regulates star formation and galaxy growth. First of all, the IGM is the reservoir of baryons from which galaxies form and it is the fuel necessary for sustaining star formation, while at the same time it is being replenished with both newly accreted intergalactic gas and chemically enriched materials from galaxies, carrying the imprints of galactic feedback. In this context, the IGM metal enrichment has gained a lot of interest after the second half of the ’90s. In fact, it was originally thought that the gas infalling onto galaxies had a primordial composition, as heavy el- ements can be produced only inside stars and star formation is not present in the low-density and high-temperature IGM. With the advent of high-resolution spectroscopy around 1995, the first metal absorption lines were observed in Quasars (QSOs) spectra, leading to the question of the mechanisms polluting the IGM. In this thesis work, I tried to characterise the properties of the IGM around galaxies at high redshift using hydrodynamical simulations compared with observational data taken from the literature. In particular, with my re- search I have shed some light on the nature of the enviroment that give rise to the observed metal systems (in particular systems identified by the C iv and Si iv transitions) and at the same time I have found that some of the subgrid physical processes implemented in simulations do not have a substantial influence on the characteristics of the IGM.