Dark matter and angular momentum in nearby disc galaxies

Dark matter and angular momentum are key parameters regulating the evolution of galaxies through cosmic time: they largely control their mass, size, and morphology. In this thesis, we have exploited exquisite observations and state-of-the-art analysis tools to robustly measure the motions of the gas in galaxies, which in turn allows us to infer their dark matter and angular momentum.
In the first part of the thesis, we studied six gas-rich ultra-diffuse galaxies (UDGs). UDGs are very peculiar systems: they have similar light distributions as big spirals like the Milky Way but about 1000 times fewer stars, making them very diffuse. We found that our galaxies rotate much slower than other galaxies with similar mass in stars and gas. Moreover, our UDGs have a much lower amount of dark matter than expected, which is very challenging to explain in the Cold Dark Matter model, the currently favoured paradigm.
In the second part of the dissertation, we performed the most detailed measurements of the angular momentum on nearby galaxies to date. We discovered a new relationship between the mass, angular momentum, and gas content of disc galaxies; this is one of the tightest known scaling relations of galaxies.
Finally, we estimated the dark matter content of a sample of nearby galaxies. For the first time, we systematically accounted for the fact that their discs are not razor-thin but thick and flared, which allowed us to obtain some of the most detailed estimations of the dark matter content in nearby galaxies.