This thesis aims to enhance our understanding of galaxies by testing theoretical models of galaxy formation against observations, particularly in the cases of extreme systems which have been found... Show moreThis thesis aims to enhance our understanding of galaxies by testing theoretical models of galaxy formation against observations, particularly in the cases of extreme systems which have been found to have an excess of baryonic mass in their central regions, in the form of either supermassive black holes or stellar populations, thus harbouring "monsters" in the deep. To this end we use the EAGLE project, a suite of cosmological, hydrodynamical simulations of galaxy formation and evolution that have been calibrated to reproduce the number density and sizes of galaxies in the Universe. We find that galaxies with supermassive black holes that are much more massive than expected given their stellar mass are predicted to exist and they become overmassive through early formation and/or tidal stripping from more massive galaxies. Recent evidence for excess stellar mass in the centres of high-mass, early-type galaxies has fueled claims that the stellar initial mass function (IMF) may be variable. We test the consequences of such variations in the EAGLE model by performing two additional simulations in which the IMF becomes respectively top-heavy or bottom-heavy in high-pressure environments. The strong effects of such variations are explored in terms of scaling relations between, and within, galaxies. Show less
This thesis investigates how galaxies form and what diversifies the evolutionary histories of galaxies. The first part of this thesis describes the identification of luminous galaxies in the early... Show moreThis thesis investigates how galaxies form and what diversifies the evolutionary histories of galaxies. The first part of this thesis describes the identification of luminous galaxies in the early Universe and the follow-up study of their properties with the Very Large Telescope, ALMA and the Hubble Space Telescope. Luminous galaxies are assembling through merging of multiple components and heavy elements as carbon are already in place relatively shortly after galaxies have formed. The second part describes the study of the Lyman-alpha escape fraction of galaxies at the peak of star formation history. The Lyman-alpha escape fraction is generally low, except for rare massive galaxies with AGN activity or for low mass galaxies. This implies that Lyman-alpha radiation escapes more efficiently in the early Universe, when galaxies tend to be less massive with a lower dust content. The final part of this thesis is a theoretical investigation of the co-evolution of dark matter halos and galaxies in the cosmological hydrodynamical EAGLE simulation. Galaxy stellar mass growth is driven by both the mass and formation time of dark matter halos. As a result, present-day growth rates of galaxies are coherent with the long time-scale histories. Show less
This thesis investigates the structural evolution and assembly of galaxies since the first few billions years after the big bang. It makes use of the CANDELs and UVISTA galaxy surveys, the EAGLE... Show moreThis thesis investigates the structural evolution and assembly of galaxies since the first few billions years after the big bang. It makes use of the CANDELs and UVISTA galaxy surveys, the EAGLE hydrodynamical simulation as well as spectroscopy from XShooter on the VLT. Within this thesis I attempt to answer when stellar mass was assembled onto galaxies, where those stars were deposited as well as the physical mechanisms which underly that assembly. Show less
