Dark matter, gas, and stars come together throughout the universe to form dwarf, spiral, and elliptical galaxies. They subsequently evolve through star formation and feedback processes, with the importance of the mechanism varying with the galaxy's redshift and environment. Astronomers at Columbia study galaxies with observations, simulations and theory in a quest to understand the distribution and interplay of baryons and dark matter in them. Studies of the distribution of cold gas in the universe reveal the methods in which star formation fuel reaches a galaxy, and comparisons to star formation rates provide information on how efficiently this gas is consumed. The distribution and chemical composition of stars in galaxies can trace the merger history of a galaxy when combined with models. There are also active studies of the physics of the interstellar medium in galaxies, active galactic nuclei, the intergalactic medium, and laboratory studies of relevant atomic physics within Columbia's strong Extragalactic and Galactic astronomy group.
