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 (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).