Abstract

In this talk I will review the role of galaxy mergers in triggering star formation, and their effect on the interstellar medium. For many years, observations have suggested that star formation is enhanced in mergers. Recently, however, a number of IFU campaigns and HI-survey suggest that mergers also enhance the H2 budget in galaxies, whilst leaving its HI content largely unaffected. Understanding how baryons migrate between ISM phases and/or become stars is a questions that has eluded us, because of lack of sufficient resolution in our simulations or lack of sophisticated models at scales both relevant to galaxies and the ISM . I will share recently published results where we employ a comprehensive suite of parsec-scale galaxy merger simulations using FIRE , the “Feedback In Realistic Environment” physics model. This framework allows us to resolve Giant Molecular Clouds and follow feedback physical processes that regulate star formation. I will describe the ISM as a pipeline where atomic gas can cool and compress into molecular gas, but the onset of star formation can turn these ISM components into warm ionized gas, or hot gas (with temperatures above 1 million Kelvin). The net result is the build-up of a molecular gas reservoir, hand in hand, with enhanced star formation – thus providing a physical picture to H2 and HI observations. If time allows, I will describe the role of this baryon cycle in building up stellar bulges in galaxies.