"Galaxy mergers: gas flows, starbursts and active galactic nuclei."

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Although the universe may seem a vast and sparsely populated place, its dynamic nature means that galaxies regularly collide. The stars in these "galaxy mergers" rarely meet each other head-on, but the effects of gravity can have spectacular consequences for the galaxy as a whole. Computer simulations show that mergers result in both streams of material being ripped away, and large quantities of the galaxies' gas being funneled towards the galactic centre as a result of strong torque forces. These simulations have led to predictions of massive nuclear starbursts and the ignition of the central black hole. Galaxy mergers may therefore be the (or one of the) main drivers of galaxy evolution. The research proposed here aims to observationally quantify the extent of a merger on a galaxy's history and therefore better understand how important these mergers are for shaping the modern universe. By using the largest sample of galaxy mergers ever assembled, we will attempt to understand how the triggering of star formation and the activity of the black hole is regulated. For example - why do some mergers result in truly massive starbursts, yet others are relatively unaffected? Do the gas flows affect star formation throughout the galactic disk, or only in the nucleus? And what happens once the starburst is complete - does the galaxy return to its old self, or is its fuel supply exhausted? These questions will be addressed by combining our unprecedentedly large sample with both new data that will span the optical, sub-millimetre and radio regimes, plus a number of novel observational techniques.