Juggling gas and metals: exploring the role of outflows in galaxy evolution
October 19, 2017 -
3:00pm to 4:00pm
Boggs 1-90 VizLab
The cycling of gas through galactic fountains links disks to halos. Simulations enable astronomers to follow this cycle by tracking gas particles. Here I analyze the role of accretion and outflows in the growth of stellar and metal mass in a suite of twenty high-resolution simulated dwarf and spiral galaxies. These simulations agree with key observables, including the stellar mass-halo mass, Tully-Fisher, and mass-metallicity relations.
This agreement relies on strong feedback-driven outflows that drive large fractions of the metals into the circumgalactic media. In fact, in dwarf galaxies, 90% of the available metals lie outside of the galactic disk at z = 0, a fraction that decreases to ~ 1/3 in Milky Way-mass galaxies. In general, ejective feedback is increasingly important to the evolution of galaxies as halo mass decreases, and we find an effective mass loading factor that scales as circular velocity to the -2.2 power. However, recycling is common: about half the outflow mass across all galaxy masses is later re-accreted on timescales of about 1 Gyr. I will discuss how these results together elucidate and quantify how the baryon cycle plausibly regulates star formation and produces the mass-metallicity relationship.