2017ApJ...835L..10L

The O VI λλ1032, 1038 A doublet emission traces collisionally ionized gas with T~10^5.5 K, where the cooling curve peaks for metal-enriched plasma. This warm-hot phase is usually not well-resolved in numerical simulations of the multiphase interstellar medium (ISM), but can be responsible for a significant fraction of the emitted energy. Comparing simulated O VI emission to observations is therefore a valuable test of whether simulations predict reasonable cooling rates from this phase. We calculate O VI λ1032 A emission, assuming collisional ionization equilibrium, for our small-box simulations of the stratified ISM regulated by supernovae. We find that the agreement is very good for our solar neighborhood model, both in terms of emission flux and mean O VI density seen in absorption. We explore runs with higher surface densities and find that, in our simulations, the O VI emission from the disk scales roughly linearly with the star formation rate. Observations of O VI emission are rare for external galaxies, but our results do not show obvious inconsistency with the existing data. Assuming the solar metallicity, O VI emission from the galaxy disk in our simulations accounts for roughly 0.5% of supernovae heating.