  In this study we explore the complex multi-phase gas of the circumgalactic
medium (CGM) surrounding galaxies. We propose and implement a novel,
super-Lagrangian 'CGM zoom' scheme in the moving-mesh code AREPO, which focuses
more resolution into the CGM and intentionally lowers resolution in the dense
ISM. We run two cosmological simulations of the same galaxy halo, once with a
simple 'no feedback' model, and separately with a more comprehensive physical
model including galactic-scale outflows as in the Illustris simulation. Our
chosen halo has a total mass of ~10^12 Msun at z ~ 2, and we achieve a median
gas mass (spatial) resolution of ~2,200 solar masses (~95 parsecs) in the CGM,
six-hundred (fourteen) times better than in the Illustris-1 simulation, a
higher spatial resolution than any cosmological simulation at this mass scale
to date. We explore the primary channel(s) of cold-phase CGM gas production in
this regime. We find that winds substantially enhance the amount of cold gas in
the halo, also evidenced in the covering fractions of HI and the equivalent
widths of MgII out to large radii, in better agreement with observations than
the case without galactic winds. Using a tracer particle analysis to follow the
thermodynamic history of gas, we demonstrate how the majority of this cold,
dense gas arises due to rapid cooling of the wind material interacting with the
hot halo, and how large amounts of cold, ~10^4 K gas can be produced and
persist in galactic halos with Tvir ~ 10^6 K. At the resolutions presently
considered, the quantitative properties of the CGM we explore are not
appreciably affected by the refinement scheme.
