Fuelling black holes with newly accreted gas

To study many of the objects in the Universe, the typical approach in Astronomy is to investigate the light that they emit or reflect. Black holes are a challenge to this approach because light cannot escape from them. To bypass this difficulty, we study black holes indirectly, by measuring the effect of the black holes on the material (gas and stars) around them. This surrounding material emits light and can therefore be observed with our telescopes. In this project we focus on the study of supermassive black holes. These are black holes that have between 1 million to 10 billion times the mass of our Sun and reside in the centre of galaxies. The host galaxies of black holes evolve with time, together with their black holes, suggesting a symbiosis between the processes that affect the gas and stars in the galaxy and the growth and activity of the supermassive black hole. One of those processes is the interaction between galaxies. For example, we know that galaxies of different sizes merge to become one, and that often galaxies acquire fresh gas from their galaxy neighbours and environment. Gas is the essential ingredient to feed the growth of supermassive black holes and fuel the formation of new stars. This interaction process may therefore be able to significantly affect the properties of galaxies, such as how large or active their black holes are, or their ability to form new stars. However, it is not clear by how much and in what circumstances this effect can occur. Due to our observing limitations, it is also not clear if this mechanism is more important earlier in the age of the Universe, where galaxy interactions were more frequent. The goal of this project is to address these major open questions and determine how the interactions between galaxies affect the growth of the black holes and the properties of the galaxies themselves. We will: - Connect the type of galaxy interaction (e.g. merger of galaxies) to the effect seen on the stars and gas in the galaxy and on the activation of the supermassive black hole. - Evaluate how important galaxy interactions are to the total growth of supermassive black holes. - Study galaxies that are close to us to guide our search for galaxies undergoing similar processes at earlier times in the history of the Universe. The results of the project will advance our knowledge of how galaxy interactions affect gas, stars and black holes and open the door to studying more distant galaxies when the Universe was younger. Establishing a baseline to study more distance galaxies will allow us to use the James Webb Space Telescope or the upcoming Extremely Large Telescope, for example, to their fullest capabilities. These future studies will determine if the physical processes or their impact on star formation and black hole growth are enhanced at earlier times when active black holes are thought to have a crucial role on galaxy evolution.