Resolving supermassive black hole binaries and AGN with GRAVITY+

Large galaxies grow through a combination of steady inflow of gas as well as major and minor mergers. As part of galaxy mergers, it is thought that the central supermassive black holes approach each other and eventually form a single black hole in the centre of the new galaxy. However, hydrodynamic simulations imply that on scales of about 1 parsec the merging process slows down as classical processes of angular momentum and energy removal are inefficient. Yet, a multitude of observational searches over the last decade for parsec-scale binary supermassive black holes (BSMBHs) came up with few
confirmed candidates. Are we looking for the right phenomena? Do BSMBHs have a way to effectively bypass the parsec-scale angular momentum barrier? And can we identify them amongst the general AGN population? Solving these questions requires a combination of state-of-the-art radiation hydrodynamical simulations and high angular resolution observations. In this PhD project, the student will contribute to cutting edge projects in both theory and observations, perfectly suiting her experience in both areas. She will work on new 3D radiation hydrodynamical simulations of the sub-parsec-scale environment of single and binary AGN (Williamson et al., in prep) to predict observables differentiating single and double AGN and will be able to test her predictions as part of the host group's involvement in consortium delivering the new GRAVITY+ interferometer at the VLTI. She will become a member of the GRAVITY+ science team and contribute to one of the main science cases of the new instrument.