PhD Thesis Defense by Nils Henrik Rhodin
Supervisor: Assoc. Prof. Lise Bech Christensen
External examiners: Dr. Valentina D'Odorico and Prof. Tom Theuns
Title: Deep Emission Studies of High Redshift Absorption Selected Galaxies: Probing the Galaxy Population With Beacons From Afar
Abstract: A major goal in modern astrophysics is to understand how galaxies form and evolve. Normally, this is done by imaging a field of the sky and studying the objects detected. The drawback with such methods is a bias against objects that are too faint to be captured by telescopes. In my thesis, I attempt to push beyond such a “luminosity bias”. Instead, I have studied galaxies selected on gas cross-section. When these objects intervene sightlines to even more distant quasars, they produce characteristic absorption and essentially appear to us as cosmic silhouettes. My results from two observational campaigns and one study on simulations confirm that this technique is efficient at selecting low mass, faint galaxy populations – which presumably are the most abundant galaxies in the Universe. In addition, it reveals that complementary information from absorption and emission can provide insights to the underlying conditions that drive star formation, metal enrichment and galaxy evolution.