Bursting Bubbles: Clustered Supernova Feedback in Local and High-redshift Galaxies

We compare an analytic model for the evolution of supernova-driven superbubbles with observations of local and high-redshift galaxies, and the properties of intact H i shells in local star-forming galaxies. Our model correctly predicts the presence of superwinds in local star-forming galaxies (e.g., NGC 253) and the ubiquity of outflows near z ∼ 2. We find that high-redshift galaxies may "capture" 20%–50% of their feedback momentum in the dense ISM (with the remainder escaping into the nearby CGM), whereas local galaxies may contain ≲10% of their feedback momentum from the central starburst. Using azimuthally averaged galaxy properties, we predict that most superbubbles stall and fragment within the ISM, and that this occurs at, or near, the gas scale height. We find a consistent interpretation in the observed H i bubble radii and velocities, and predict that most will fragment within the ISM, and that those able to break out originate from short dynamical time regions (where the dynamical time is shorter than feedback timescales). Additionally, we demonstrate that models with constant star cluster formation efficiency per Toomre mass are inconsistent with the occurrence of outflows from high-z starbursts and local circumnuclear regions.