2006PASJ...58..641Y

The time evolution of the ionization state of metals in cosmic baryons is considered in a cosmological context without the assumption of ionization equilibrium. We find that a significant fraction of ionized oxygen (O <FONT SIZE="-2">VII</FONT> and O <FONT SIZE="-2">VIII</FONT>) in a warm-hot intergalactic medium (WHIM) is not in the ionization equilibrium state at a redshift of z ≃0. We also investigate the effect on the detectability and observables of WHIM as a consequence of such a deviation from ionization equilibrium. It is found that the detectability of WHIM is not altered very much both through its emission and absorption signatures, but the line ratios between O <FONT SIZE="-2">VII</FONT> and O <FONT SIZE="-2">VIII</FONT> are significantly different from those in the ionization equilibrium state.