Ion column density distribution of co-located O VI and O VII in EAGLE (gray histogram in the background). The orange contours show the percentiles of N_OVII that are counterparts to O VI absorbers with mean ion-weighted O VI temperature > 10^6.1 K (hot phase) as a function of the total (i.e., for all phases) O VI column density. The blue contours show the same for T_OVI < 10^6.1 K (warm phase). The pink bars indicate the FUV measured warm O VI column density 1σ uncertainty range, whereas the red point marks the total ion columns of the two–phase model (i.e., hot and warm O VI, hot O VII). The green lines mark the approximate detection thresholds for O VI and O VII in FUV and X-ray bands. Detection thresholds for two representative X-ray instruments are shown: the RGS camera on-board XMM-Newton, and the Athena X-IFU, currently under development.