How Do Supernovae-Driven Outflows Shape the Multiphase Circumgalactic Medium?

Miao Li (CCA)
Friday, November 15, 2019 - 12:15pm to 1:00pm

Supernovae (SNe) drive metal-enriched, galaxy-wide outflows. How the outflows impact the circumgalactic medium (CGM) depends on (a) how much mass/energy/metals the outflows carry, and (b) what is already in the CGM. Small-box, high-resolution simulations on SNe feedback constrain (a) but leave out (b), whereas cosmological simulations capture (b) but often use ad hoc models for (a).  We aim at bridging the gap by adopting small-box results as the outflow model for galaxy-scale simulations to study the resultant CGM. In this talk, I will first summarize the recent progress of small-box simulations; particularly, the hot outflows are much more powerful than cool outflows while also appear very simple. Using a Milky Way-mass galaxy for an example, we find that, when the star formation surface density is low, hot outflows form large-scale fountains in the halo. The warm-hot CGM has a universal density profile, which produces the observed column density of O VI, VII, and VIII, and X-ray emission. Cool gas condenses out of the hot CGM and falls toward the galaxy. In contrast, when the star formation surface density is high, the outflows are bipolar in shape and funnel metals into the intergalactic medium; cool phase is formed en route, with a fraction moving outward at several hundred km/s at large radii.

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