CCA Short Talks (Ben Oppenheimer)

High vs. Low, Active vs. Passive: Contrasting Opposites in the Circumgalactic Medium

Benjamin D. Oppenheimer
University of Colorado

The multi-ion circumgalactic survey of COS-Halos has quantified the distribution of metal column densities around the diversity of star-forming and passive galaxies in the evolved Universe. I will present EAGLE zoom simulations of the circumgalactic medium (CGM) probing the gaseous halos around a range of spiral, L* galaxies and elliptical, quenched galaxies. Why do high ions, like O VI, appear strong only around the former, but low ions, like C II and Si III, appear the same around both types? I will present the answers from simulations that while not simple, will fit into a 30-minute talk. The preview of the answers include that the CGM 1) has at least two phases, 2) shows ions dependent on the halo virial temperature, and 3) may constantly be out of ionization equilibrium.