Bursting Bubbles: Feedback from Clustered SNe and the Trade-off Between Turbulence and Outflows

TL;DR

This paper develops an analytic model for clustered supernova feedback in galaxy disks, showing how superbubbles either stall or break out, influencing galactic turbulence, outflows, and star formation relations.

Contribution

It introduces a realistic model for superbubble evolution from clustered SNe, linking superbubble behavior to galaxy-scale feedback effects and star formation laws.

Findings

Superbubbles almost always break out before the last SN in a cluster.

The transition between stalling and breakout affects galaxy turbulence and outflow strength.

Feedback effectiveness changes at a critical point, impacting star formation scaling laws.

Abstract

We present an analytic model for clustered supernovae (SNe) feedback in galaxy disks, incorporating the dynamical evolution of superbubbles formed from spatially overlapping SNe remnants. We propose two realistic outcomes for the evolution of superbubbles in galactic disks: (1) the expansion velocity of the shock front falls below the turbulent velocity dispersion of the ISM in the galaxy disk, whereupon the superbubble stalls and fragments, depositing its momentum entirely within the galaxy disk, or (2) the superbubble grows in size to reach the gas scale height, breaking out of the galaxy disk and driving galactic outflows/fountains. In either case, we find that superbubble breakup/breakout almost always occurs before the last Type-II SN ($\lesssim$40 Myr) in the recently formed star cluster, assuming a standard high-end IMF slope, and scalings between stellar lifetimes and masses. The threshold between these two cases implies a break in the effective strength of feedback in driving turbulence within galaxies, and a resulting change in the scalings of, e.g., star formation rates with gas surface density (the Kennicutt-Schmidt relation) and the star formation efficiency in galaxy disks.