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 halo > 10 11 M . 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-α 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.

We analyze the mass, temperature, metal enrichment, and OVI abundance of the circumgalactic medium (CGM) around z ∼ 0.2 galaxies of mass 10 9 M < M < 10 11.5 M in the Illustris simulation. Among star-forming galaxies, the mass, temperature, and metallicity of the CGM increase with stellar mass, driving an increase in the OVI column density profile of ∼ 0.5 dex with each 0.5 dex increase in stellar mass. Observed OVI column density profiles exhibit a weaker mass dependence than predicted: the simulated OVI abundance profiles are consistent with those observed for starforming galaxies of mass M = 10 10.5−11.5 M , but underpredict the observed OVI abundances by 0.8 dex for lower-mass galaxies. We suggest that this discrepancy may be alleviated with additional heating of the abundant cool gas in low-mass halos, or with increased numerical resolution capturing turbulent/conductive mixing layers between CGM phases. Quenched galaxies of mass M = 10 10.5−11.5 M are found to have 0.3-0.8 dex lower OVI column density profiles than star-forming galaxies of the same mass, in qualitative agreement with the observed OVI abundance bimodality. This offset is driven by AGN feedback, which quenches galaxies by heating the CGM and ejecting significant amounts of gas from the halo. Finally, we find that the inclusion of the central galaxy's radiation field may enhance the photoionization of the CGM within ∼ 50 kpc, further increasing the predicted OVI abundance around star-forming galaxies.

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