Launching of hot gas outflow by disc-wide supernova explosions
  Galactic gas outflows are driven by stellar feedback with dominant
contribution from supernovae (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 in the range from
{$\simeq 6\times 10^{-4}$ to $\simeq 6\times
10^{-2}~M_\odot$~yr$^{-1}$~kpc$^{-2}$, corresponding to mid-to-high star
formation observed in galaxies. We show that such disc-wide SN explosion regime
can form circulation of warm ($T\sim 10^4$ K) and cold ($T<10^3$ K) phases
within a few gas scale heights, and elevation of hot {($T>10^5$ K)} gas at
higher ($z>1$ kpc) heights. We found that the threshold energy input rate for
hot gas outflows with disc-wide supernovae explosions is estimated to be of the
order $\sim 4\times 10^{-4}$~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 ($\Sigma_{_{\rm
SF}}>0.02~M_\odot$~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 SF rates ($\Sigma_{_{\rm
SF}}>0.006~M_\odot$~yr$^{-1}$~kpc$^{-2}$) can be bright, with a smooth surface
brightness in low-energy bands ($0.1\hbox{--}0.3$~keV) and patchy at higher
energies ($1.6\hbox{--}8.3$~keV).}
