We investigated the impact of supernova feedback in gas-rich dwarf galaxies experiencing a low-to-moderate star formation rate, typical of relatively quiescent phases between starbursts. We calculated the long term evolution of the ISM and the metal-
rich SN ejecta using 3D hydrodynamic simulations, in which the feedback energy is deposited by SNeII exploding in distinct OB associations. We found that a circulation flow similar to galactic fountains is generally established, with some ISM lifted at heights of one to few kpc above the galactic plane. This gas forms an extra-planar layer, which falls back to the plane in about $10^8$ yr, once the star formation stops. Very little or no ISM is expelled outside the galaxy system for the considered SFRs, even though in the most powerful model the SN energy is comparable to the gas binding energy. The metal-rich SN ejecta is instead more vulnerable to the feedback and we found that a significant fraction (25-80%) is vented in the intergalactic medium, even for low SN rate ($7times 10^{-5}$ - $7times 10^{-4}$ yr$^{-1}$). About half of the metals retained by the galaxy are located far ($z >$ 500 pc) from the galactic plane. Moreover, our models indicate that the circulation of the metal-rich gas out from and back to the galactic disk is not able to erase the chemical gradients imprinted by the (centrally concentrated) SN explosions.
In this study we present three-dimensional radiative cooling hydrodynamical simulations of galactic winds generated particularly in M82-like starburst galaxies. We have considered intermittent winds induced by SNe explosions within super star cluster
s randomly distributed in the central region of the galaxy and were able to reproduce the observed M82 wind conditions with its complex morphological outflow structure. We have found that the environmental conditions in the disk in nearly recent past are crucial to determine whether the wind will develop a large scale rich filamentary structure, as in M82 wind, or not. Also, the numerical evolution of the SN ejecta have allowed us to obtain the abundance distribution over the first 3 kpc extension of the wind and we have found that the SNe explosions change significantly the metallicity only of the hot, low-density wind component. Moreover, we have found that the SN-driven wind transports to outside the disk large amounts of energy, momentum and gas, but the more massive high-density component reaches only intermediate altitudes smaller than 1.5 kpc. Therefore, no significant amounts of gas mass are lost to the IGM and the mass evolution of the galaxy is not much affected by the starburst events occurring in the nuclear region.
The ejection of the gas out of the disk in late-type galaxies is related to star formation and is due mainly to Type II supernovae. In this paper we studied in detail the development of the Galactic fountains in order to understand their dynamical ev
olution and their influence in the redistribution of the freshly delivered metals over the disk. To this aim, we performed a number of 3D hydrodynamical radiative cooling simulations of the gas in the Milky Way where the whole Galaxy structure, the Galactic differential rotation and the supernovae explosions generated by a single OB association are considered. A typical fountain powered by 100 Type II supernovae may eject material up to $sim 2$ kpc which than collapses back mostly in form of dense, cold clouds and filaments. The majority of the gas lifted up by the fountains falls back on the disk remaining within a radial distance $Delta R=0.5$ kpc from the place where the fountain originated. This localized circulation of disk gas does not influence the radial chemical gradients on large scale, as required by the chemical models of the Milky Way which reproduce the metallicity distribution without invoking large fluxes of metals. Simulations of multiple fountains fuelled by Type II supernovae of different OB associations will be presented in a companion paper.
