MOlecules as Probes of the Physics of EXternal galaxies

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Molecules pervade the cooler, denser parts of our Universe, in particular the reservoirs of the matter that forms stars and planets, and the gas in the centres of galaxies. In the Milky Way we routinely use molecules to discover and explore these regions and the more complex the chemistry, the more details of the gas the molecules reveal. There are one hundred billion galaxies in the observable Universe. About 200 or so are our neighbours. However, due to their distance, we are still not able to zoom in and observe individual clouds of dense gas. Nevertheless with the advent of ever more sensitive telescopes such as ALMA, we are discovering that chemistry in external galaxies is as complex as in our own Milky Way. Molecules, it seems, are universal and widespread. In MOPPEX I use molecules to shed light on the physical and chemical structure of our local galaxies, namely (i) what the energetic processes that determine their appearance are and (ii) where the matter that will form stars or fuels black holes is, with the ultimate goal to understand how galaxies form, evolve and interact with each other. To achieve this objective I propose a multi-faceted program that combines state of the art chemical and statistical models in conjunction with interferometric observations. More specifically, the success of MOPPEX relies on (i) in-house and open source suites of chemical models and an in-house line radiative transfer model, (ii) a new suite of tools comprising of modular statistical and machine learning algorithms, and (iii) large datasets of observational data on two nearby galaxies differing in types. My ultimate objective is to fundamentally change the way molecular observations are interpreted for external galaxies and thus to cause a paradigm shift in the use of molecules as tools to determine the chemistry and physics of galaxies.