Fredagskollokvium: The circumgalactic gas and metals around star forming and elliptical galaxies

Understanding the baryon cycle in galaxies, i.e., how gas is accreted onto galaxies,
consumed in star formation, and ejected back to the environment is one of the forefront goals in modern galaxy formation theory.  Studies of the distribution, kinematics and evolution of the gas and metals in the circumgalactic medium (CGM) provide clues to understanding the baryon cycle. In this talk, I will first overview recent progress on observational and numerical studies on the CGM. I will then present results on the distribution and evolution of the circumgalactic gas and metals around massive galaxies at z=0-3 from two suites of galaxy formation simulations, and detailed comparisons with observed Lyman alpha and metal absorption data. I will discuss the origins of cold, enriched gas in the CGM probed by low ionisation metallic ions, and its correlation with the warm-hot gas probed by O VI. I will then explore how feedback from supernova and the active galactic nuclei (AGN) affect the circumgalactic gas and metal distributions.