Bimodality of low-redshift circumgalactic O vi in non-equilibrium eagle zoom simulations

We introduce a series of 20 cosmological hydrodynamical simulations of L* (M-200 = 10(11.7)-10(12.3) M-aS (TM)) and group-sized (M-200 = 10(12.7)-10(13.3) M-aS (TM)) haloes run with the model used for the eagle project, which additionally includes a non-equilibrium ionization and cooling module that follows 136 ions. The simulations reproduce the observed correlation, revealed by COS-Halos at z similar to 0.2, between column density at impact parameters b < 150 kpc and the specific star formation rate (sSFR a parts per thousand SFR/M-*) of the central galaxy at z similar to 0.2. We find that the column density of circumgalactic is maximal in the haloes associated with L* galaxies, because their virial temperatures are close to the temperature at which the ionization fraction of peaks (T similar to 10(5.5) K). The higher virial temperature of group haloes (> 10(6) K) promotes oxygen to higher ionization states, suppressing the column density. The observed 1 and much of the ejected metal mass resides beyond the virial radius of galaxies. For both L* and group galaxies, more of the oxygen produced and released by stars in the circumgalactic medium (within twice the virial radius) than in the stars and interstellar medium of the galaxy.