Galactic Winds

Gas ejected from stars in elliptical galaxies is heated by supernova explosions and produces outward- flowing galactic winds. Except possibly for the dust component, steady-state galactic winds are impossible to observe. However, some galactic winds have thermally unsteady cores which can be observed in optical emission lines. If the gas which is thermally unsteady remains ionized as it goes into free fall at the galactic center, objects more massive than stars tend to form. It is likely that nonthermal radio emission and optical line emission can occur only in those ellipticals with thermally unsteady galactic winds.