Ionized gas velocity dispersion and multiple supernova explosions

Using 3D numerical simulations we study the evolution of the H$\alpha$ intensity and velocity dispersion for single and multiple supenova (SN) explosions. We find that the $I_{\rm H\alpha}-\sigma$ diagram obtained for simulated gas flows is similar in shape to that observed in dwarf galaxies. We conclude that colliding SN shells with significant difference in age are resposible for high velocity dispersion that reaches values high as $\simgt 100$kms$^{-1}$. Such a high velocity dispersion could be hardly got for a single SN remnant. Peaks of velocity dispersion on the $I_{\rm H\alpha}-\sigma$ diagram may correspond to several stand-alone or merged SN remnants with moderately different ages. The procedure of the spatial resolution degrading in the H$\alpha$ intensity and velocity dispersion maps makes the simulated $I_{\rm H\alpha}-\sigma$ diagrams close to those observed in dwarf galaxies not only in shape, but also quantitatively.