Absorption spectroscopy as a unique probe of galaxy evolution

Our understanding of galaxy evolution cannot be complete without characterizing the ISM properties throughout cosmic time. In particular, the chemical enrichment of the ISM plays a crucial role in the cooling processes that lead to star formation. Moreover, the build up of metals in the ISM is related to the feedback from star formation and AGN. Hence, constraining the chemical evolution of gas in galaxies provides important clues for models and simulations of galaxy evolution.
I will demonstrate how, at cosmological distances, the ISM is best studied in absorption seen towards bright background sources. Since the detection of absorption systems depends on the gas cross-section and not on the luminosity of the associated galaxies, this technique allows us to probe much fainter galaxies than what is observed in flux-limited surveys at high redshift. In this talk I will present recent results highlighting the strength of absorption-selected galaxies as a cosmological tool. Lastly, I will discuss current issues and relate those to future missions which will be imperative for the advancement of the field.