The evolution of the atomic and molecular interstellar medium in star-forming galaxies

In this thesis I developed models to make predictions for the atomic and molecular gas content of galaxies. Main results of my thesis include that the atomic hydrogen content of galaxies remained relatively constant with over the last 10 Billion years, whereas the molecular hydrogen content decreased by more than an order of magnitude during the same cosmic epoch. I furhermore found that the decline in the cosmic star-formation rate of our Universe is driven by a decrease in the gas content of galaxies, and by a decrease in the fraction of gas in galaxies that is eligible for star-formation. I also developed models that make predictions for the emission of atoms and molecules such as carbon, oxide, and carbonmonoxide. The results presented in this thesis will be extremely useful for future surveys with the newest generation of radio and sub-mm telescopes such as ALMA in Chile and the SKA in South-Afrika and Australia