Published online by Cambridge University Press: 12 April 2016
Recent developments, both observational and theoretical, require a reevaluation of the effects of clustered supernovae on the two-dimensional porosity parameter Q2D and the rates of mass injection into the halo Ṁ of both cold and hot gas. Clustered supernovae produce two types of bubble. Most clusters produce breakthrough bubbles, which do no more than break through the dense gas disk. But large clusters produce enough energy to make blowout bubbles, which blow gas up into the halo. We calculate area filling factors and mass injection rates into the halo for different types of galaxy. We relate our calculations to two observables, the area covered by H I ‘holes’ and the area covered by giant H II regions. We also reiterate the difficulty of producing the very largest supershells by clusered supernovae.