Title: How Do Supernovae-driven Galactic Outflows Impact the Circumgalactic Medium?

Speaker:Dr. Miao Li (Flatiron Institute)

Date:Thursday, July 04, 2019, 02:00pm

Venue:South 727, Mong Man-wai Science Technology Building


Abstract:The missing baryon and the missing metals problems are the two major challenges for galaxy formation. Circumgalactic Medium (CGM), where cosmic inflows interact with galactic outflows, bears critical information for solving these problems. Cosmological simulations can model cosmic inflows but their galactic outflows rely on ad hoc sub-grid models, thus unable to predict CGM from first principles. The path forward requires better understanding the feedback physics and using physically-based models in large-scale simulations. In this talk, I will first summarize our results on supernovae (SNe) feedback using parsec-resolution, small-box simulations, where we quantify the energy/mass/metal fluxes of SNe-driven outflows from the interstellar medium. Then, I will introduce our galactic scale simulations focusing on the CGM, which adopt the outflow models from the small-box simulations. Using Milky-Way mass galaxy as an example, we find that the CGM around galaxies with low star formation rate is qualitatively different from that with high star formation rate, where the hot outflows change from gravitationally bound to unbound. For the former, hot outflows form a spherical, metal-enriched atmosphere, which naturally produces the observed column density of O VI, VII, VIII, and X-ray emissions. Cool gas precipitates down once the hot atmosphere becomes “saturated”. For the latter, the hot outflows break out in bipolar directions, form cool outflowing gas along the way, and funnel metals into the intergalactic medium. I will discuss the implications of our results to the missing baryon and the missing metals problems.