Monday

The advent of extra-galactic surveys that are both deep and wide (e.g. LSST) is poised to revolutionise the study of galaxy evolution, by revealing aspects of galaxies and their environments that are invisible in past datasets. For example, these surveys will reveal low-surface-brightness tidal features that encode galaxy merger histories, enable studies of the inter-galactic medium and the faint outskirts of local systems, and truly open up the realm of dwarf galaxies. In this talk I will focus on the role of ‘minor’ mergers - i.e. mergers with unequal mass ratios - in driving galaxy evolution. Minor mergers produce faint tidal features that are invisible in past surveys like the SDSS. However, using data from the SDSS Stripe 82, I will argue that the persistence and ubiquity of this process over cosmic time makes it a fundamental (but largely unexplored) driver of galaxy evolution. I will show that around half of all the stellar mass growth in the local Universe likely takes place when galaxies are undergoing a minor merger, and show that this process promotes nuclear accretion and therefore the growth of BHs. Surveys like LSST (and precursors like DECaLS and the Hyper Suprime Cam Survey) will enable us, for the first time, to quantify the influence of this key process in the evolution of the observable Universe.