Abstract
Over the past century, extragalactic astronomy has undergone significant developments, enabling the study of galaxy formation across a vast range of spatial and temporal scales. The evolution of galaxies through cosmic time is driven by a complex interplay between a number of factors, including baryonic physics, feedback from stars and black holes, interactions with other galaxies, and environmental effects. Consequently, the observed galaxy population in the Universe is remarkably diverse. The sizes, masses, colours, and morphologies of galaxies are primarily determined by their stellar and gaseous contents, environments, and evolutionary histories. The emergence of scaling relations indicates the presence of fundamental laws that regulate the complex and intertwined evolution of these pivotal galaxy properties. Furthermore, the observed scatter around the average relations raises the question of what processes are involved in the formation of galaxies with extreme properties. Starburst galaxies represent the most intensely star-forming outliers above the star-forming main sequence, which correlates star formation rates of galaxies with their stellar masses. It remains uncertain whether starbursts are predominantly driven by the presence of particularly large gas reservoirs to fuel star formation or by an enhanced efficiency in converting gas into stars. Moreover, it is established that the merging of gas-rich galaxies can result in enhanced star-formation rates, due to the concentration of gas in their central regions. Nevertheless, not all starbursts are linked to mergers, which gives rise to the question of what are the driving mechanisms behind a starburst. In general, starburst events, and the processes associated with their onset and ending, may have dramatic effects on the kinematics of stars and gas in the central regions of galaxies and on morphological structures.
In this thesis, I will summarize my work on the origin and evolution of starburst galaxies from the perspective of cosmological hydrodynamical simulations, carried out at the University of Zurich, under the supervision of Prof. Dr. Robert Feldmann. Chapter 1 is dedicated to a broad introduction to extragalactic astronomy and starburst galaxies. I will then give an overview of numerical methods and results from galaxy formation simulations in Chapter 2 and Chapter 3. Chapter 4 describes the sub-grid physics models and the FIREbox simulation. In Chapter 5, I will report our results and conclusions from our work on the nature of starburst galaxies. We analyse galaxies from the FIREbox cosmological volume at redshifts z=0-1 and show that central gas compaction is the primary driver of starbursts, associated with either galaxy interactions or gravitational instabilities. Starburst events might therefore play an important role in inducing the formation central galactic structures and stellar bulges. In Chapter 6, I will summarize our work on the formation of kinematically misaligned discs in galaxies, induced by starbursts that cause the depletion of their pre-existing co-rotating gas disc. Finally, the effect of either strong stellar feedback or starburst-induced black hole feedback is thought to be crucial in driving the transition from star-forming to quenched galaxies and possibly originating post-starburst galaxies. Chapter 7 focuses on preliminary work on the properties of z=0.7 PSB candidates in FIREbox, that aims at providing constraints on the fraction of misidentified, impostor PSBs in observations and the role of different quenching mechanisms in producing a realistic population of PSBs in simulations.
Cenci, Elia