Launching of hot gas outflow by disc-wide supernova explosions

ABSTRACT 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 ($\Sigma _{_{\rm SF}}\gt 0.02~\mathrm{ M}_\odot$ 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 ($\Sigma _{_{\rm SF}}\gt 0.006~\mathrm{ M}_\odot$ 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).