The hierarchy probe · Galaxy Evolution: Solving the hierarchy problem with powerful AGN

Understanding the physical processes that shaped galaxies in the Universe is a key goal of astrophysics. However, we face a fundamental problem between the disciplines of theory and observations in explaining the characteristics of massive galaxies (“The Hierarchy Problem”). Theoretical models suggest that galaxies evolve though hierarchical mergers in a gradual assembly of galaxies which is thought to induce contemporary starburst activity from the interacting gas and dust. However, we also know early-type galaxies are characterized by their deficiency in the large quantities of cool dust and gas associated with mergers and needed for star formation. We are then left with the following fundamental problem: In the context of galaxy evolution through hierarchical mergers, what inhibits star formation and galaxy growth in massive, early-type galaxies?A popular, but still unproven, way of solving this question is by ‘AGN feedback’. In galaxy mergers, large amounts of dust and gas maybe funneled down towards the galactic cores triggering an AGN. In turn the AGN can then produce intense nuclear emission and collimated jets that will influence the AGN galaxies local environments, star formation histories through excitation and ionization of the Inter Stellar Medium (ISM).The fact that AGN may play such a critical role in galaxy evolution is not reflected in our understanding of these objects. To address this problem, in close collaboration with researchers at IAS, I have developed a science program which will allow us together to address the key question of the triggering mechanism for AGN and the star formation evolution of the host galaxy, using data from the latest state of the art observatories available to us (Herschel, IRAM, ATCA). Due to the uniqueness of the data available to us and expertise in the team that I will work the result are anticipated to be key for are understanding of galaxy evolution over cosmic time.