Sijing Shen - April 5, 2018 Circumgalactic O VI around z ~ 0 L* galaxies in cosmological zoom-in simulations We present results on the origins, distribution and kinematics of O VI absorbers around star-forming L* galaxies at z ~ 0 from detailed comparisons between the high-resolution zoom-in simulation "Eris" and the COS-Halos data. At z ~ 0, the O VI column density is between 10^14 to 10^15 cm^-2 up to virial radius, consistent with the COS-halo observations. This column density appears to remain unchanged from z = 3 to z = 0 in the range of 10-100 kpc. The 3D mass distribution of the circumgalactic OVI peaks at the virial radii for all redshifts. We identify two origins of the OVI gas at z = 0: within ~ 100 kpc, majority of the gas traced by O VI is warm-hot gas with pressure of 10 < P < a few 100 cm^-3 K, and they are mainly collisionally ionised. At larger radii, however, gas pressure is around 1 cm^-3 K and O VI is in photoionisation equilibirum with the UV background. At high redshift (z>1), collisional ionisation dominates for the entire CGM. We track gas particles with high O VI abundances at z = 0 back to z = 3 to identify its origins, and find that it is predominately from cooling of hot (T >~ 10^6) corona gas. However, unlike the classical interpretation of hot mode shock accretion, the corona gas is mainly heated by energy injected from supernova feedback. At all redshifts, majority of the gas traced by O VI is outflowing, although the fraction of inflowing component increases with time.