Abstract
Red weather alert: dangerous cosmic weather forecast, in light of galaxy cluster mergers! One of the most fascinating discoveries in astrophysics is the fine interplay that regulates the interaction between large-scale structure, galaxy formation and black hole evolution. On the largest scales, pairs of galaxy clusters colliding drive the growth of structure. Cluster mergers are the most energetic events since the Big Bang, which release 10^64 ergs over 1-2 billion years and can produce dramatic, long lasting effects, including the largest shocks and turbulence in the Universe. I will discuss how mergers provide the ideal ecosystem where we can consistently study the interdependence and interconnection between star formation, black hole feeding and feedback, gas inflow and outflow and structure formation. For example, I recently discovered a new phenomenon in which the merger of galaxy clusters can trigger the formation of new stars in cluster galaxies. With approximately half the galaxy clusters in the local Universe undergoing mergers, this work revealed significant gaps in our understanding of the growth of structure in the Universe and showed the potential for discovery in this understudied field. By bringing together multiwavelenth data spanning from the radio to the X-ray, I will discuss how merger shocks and turbulence shape the evolution of cluster galaxies and reverse typical environmental trends. Peering into galaxy and black hole evolution at the epoch when structures first formed, a treasure trove of merging cluster samples at increasingly large redshifts will be delivered by instruments such as Lynx, LOFAR, SKA and GMT. I will highlight how shock-induced star formation may be a fundamental driver not only in the evolution of low redshift clusters, but also in the context of proto-clusters and high-redshift clusters, where mergers and shocks were far more common than in the nearby Universe.