The Impact of Galactic Feedback on the Circumgalactic Medium
  Galactic feedback strongly affects the way galactic environments are
enriched. We examine this connection by performing a suite of cosmological
hydrodynamic simulations, exploring a range of parameters based on the galaxy
formation model developed in Vogelsberger et al. 2013 (henceforth V13). We
examine the effects of AGN feedback, wind mass loading, wind specific energy,
and wind metal-loading on the properties of the circumgalactic medium (CGM) of
galaxies with $M_\text{halo} > 10^{11} M_\odot$. Note that while the V13 model
was tuned to match observations including the stellar mass function, no
explicit tuning was done for the CGM. The wind energy per unit outflow mass has
the most significant effect on the CGM enrichment. High energy winds launch
metals far beyond the virial radius. AGN feedback also has a significant
effect, but only at $z < 3$. We compare to high redshift HI and CIV
observations. All our simulations produce the observed number of Damped
Lyman-$\alpha$ Absorbers. At lower column density, several of our simulations
produce enough Lyman Limit Systems (LLS) $100$ kpc from the galaxy, but in all
cases the LLS abundance falls off with distance faster than observations, with
too few LLS at $200$ kpc. Further, in all models the CIV abundance drops off
too sharply with distance, with too little CIV $100$-$200$ kpc from the galaxy.
Higher energy wind models produce more extended CIV but also produce less
stars, in tension with star-formation rate density observations. This
highlights the fact that circumgalactic observations are a strong constraint on
galactic feedback models.
