Observing and Simulating Galaxy Evolution - from X-ray to Millimeter Wavelengths

What main mechanisms set the star formation rate (SFR) of galaxies? This PhD thesis is a quest into the influences of gas and Active Galactic Nuclei (AGNs) on the SFR, with particular focus on massive galaxies at z~2. First, a new code if presented; SImulator of GAlaxy Millimeter/submillimeter Emission (S\'IGAME) which can predict the atomic/molecular line emission from galaxies. By post-processing the outputs of cosmological simulations of galaxy formation with sub-grid physics recipes, S\'IGAME divides the Interstellar Medium (ISM) into different gas phases and derives density and temperature structure, with locally resolved radiation fields. This method is used to predict the strengths of CO rotational transitions as well as the [CII] emission line in normal star-forming galaxies at z~2. A CO ladder close to that of our own Galaxy is found, but with CO-H2 conversion factors about 3 times smaller. For a set of 7 simulated galaxies at z~2, the relation between [CII] luminosity and SFR displays a slope significantly steeper than that found for observed galaxies at z