We present an analysis of the galaxy-scale gaseous outflows from the FIRE ( Feedback in Realistic Environments ) simulations .
This suite of hydrodynamic cosmological zoom simulations resolves formation of star-forming giant molecular clouds to z = 0 , and features an explicit stellar feedback model on small scales .
Our simulations reveal that high redshift galaxies undergo bursts of star formation followed by powerful gusts of galactic outflows that eject much of the ISM and temporarily suppress star formation .
At low redshift , however , sufficiently massive galaxies corresponding to L*-progenitors develop stable disks and switch into a continuous and quiescent mode of star formation that does not drive outflows far into the halo .
Mass-loading factors for winds in L*-progenitors are \eta \approx 10 at high redshift , but decrease to \eta \ll 1 at low redshift .
Although lower values of \eta are expected as halos grow in mass over time , we show that the strong suppression of outflows with decreasing redshift can not be explained by mass evolution alone .
Circumgalactic outflow velocities are variable and broadly distributed , but typically range between one and three times the circular velocity of the halo .
Much of the ejected material builds a reservoir of enriched gas within the circumgalactic medium , some of which could be later recycled to fuel further star formation .
However , a fraction of the gas that leaves the virial radius through galactic winds is never regained , causing most halos with mass M _ { h } \leq 10 ^ { 12 } \mathrm { M } _ { \odot } to be deficient in baryons compared to the cosmic mean by z = 0 .