Launching of hot gas outflow by disc-wide supernova explosions

Galactic gas outflows are driven by stellar feedback with dominant contribution from supernova (SN) explosions. The question of whether the energy deposited by SNe initiates a large-scale outflow or gas circulation on smaller scales - between discs and intermediate haloes - depends on SN rate and their distribution in space and time. We consider here gas circulation by disc-wide unclustered SNe with galactic star formation rate (SFR) in the range from ≃6 × 10^-4 to ≃6 × 10^-2 M_⊙ yr^-1 kpc^-2, corresponding to mid-to-high star formation (SF) observed in galaxies. We show that such disc-wide SN explosion regime can form circulation of warm (T ∼ 10⁴ K) and cold (T < 10³ K) phases within a few gas scale heights, and elevation of hot (T > 10⁵ K) gas at higher (z > 1 kpc) heights. We found that the threshold energy input rate for hot gas outflows with disc-wide SN explosions is estimated to be of the order ∼4 × 10^-4 erg s^-1 cm^-2. We discuss the observational manifestations of such phenomena in optical and X-ray bands. In particular, we found that for face-on galaxies with SF (Σ _{_SF}> 0.02 M_⊙ yr^-1 kpc^-2), the line profiles of ions typical for warm gas show a double-peak shape, corresponding to out-of-plane outflows. In the X-ray bands, galaxies with high SFRs (Σ _{_SF}> 0.006 M_⊙ yr^-1 kpc^-2) can be bright, with a smooth surface brightness in low-energy bands (0.1-0.3 keV) and patchy at higher energies (1.6-8.3 keV).