This prize-winning Ph.D. thesis by Chris Harrison adopts a multi-faceted approach to address
the lack of decisive observational evidence utilising large observational data sets from
several world-leading telescopes. Developing several novel observational techniques Harrison
demonstrated that energetic winds driven by Active Galactic Nuclei (AGN) are found in a large
number of galaxies with properties in agreement with model predictions. One of the key
unsolved problems in astrophysics is understanding the influence of AGN the sites of growing
supermassive black holes on the evolution of galaxies. Leading theoretical models predict that
AGN drive energetic winds into galaxies regulating the formation of stars. However until now
we have lacked the decisive observational evidence to confirm or refute these key predictions.
Careful selection of targets allowed Harrison to reliably place these detailed observations
into the context of the overall galaxy population. However in disagreement with the model
predictions Harrison showed that AGN have little global effect on star formation in galaxies.
Theoretical models are now left with the challenge of explaining these results.
