Abstract: The strong correlations that are found between supermassive black hole (SMBH) mass and velocity dispersion, stellar mass and bulge mass have long been interpreted as co-evolution of galaxies and their SMBHs through galaxy mergers. However, a flurry of new results, both observational and theoretical, have suggested that galaxy mergers may not be the dominant mechanism powering this co-evolution. I shall review these findings and present results showing that merger-free galaxies have SMBHs up to a billion solar masses and have substantial energetic outflows powered by the active galactic nuclei (AGN). In addition I will present work in collaboration with the Horizon-AGN simulation team showing that merger-free evolutionary processes also lead to co-evolution of galaxies and their SMBHs. This has interesting implications: if both galaxy-merger-driven and galaxy-merger-free SMBH growth leads to co-evolution, this suggests that co-evolution is regulated by AGN feedback in both scenarios. AGN feedback is thought to be a key regulator of co-evolution and considered necessary in cosmological volume simulations employing ΛCDM, yet the role of AGN feedback in the absence of mergers is currently unknown. I will therefore discuss the future observations needed to understand the role of this understudied merger-free co-evolution pathway.

Bio: Dr Rebecca Smethurst is a Royal Astronomical Society Research Fellow at the University of Oxford. She did her PhD at Oxford, before moving to the University of Nottingham as a research fellow for 2 years. Her work specialises in the growth of supermassive black holes and the impact of AGN feedback that results from that growth. She is part of the SDSS MaNGA and Galaxy Zoo collaborations, and was recently awarded the Royal Astronomical Society’s Winton Award for research by a post-doctoral fellow in astronomy whose career has shown the most promising development.