Any Way the Wind Blows: Quantifying Superbubbles and their Outflows in Simulated Galaxies across $z \approx 0-3$

TL;DR

This study uses FIRE-2 simulations to analyze superbubbles and multiphase outflows in galaxies at different cosmic epochs, revealing their properties, impact on the ISM and CGM, and consistency with observations.

Contribution

It provides a detailed characterization of superbubbles and outflows across redshifts, highlighting their role in galaxy evolution and methodological influences on measurements.

Findings

Outflow fluxes peak during superbubbles across all galaxies.

Mass-loading factors and momentum fluxes agree with recent observations.

Methodological choices significantly affect outflow measurement results.

Abstract

We present an investigation of clustered stellar feedback in the form of superbubbles identified within eleven galaxies from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, at both cosmic noon (1 < z < 3) and in the local Universe. We study the spatially-resolved multiphase outflows that these supernovae drive, comparing our findings with recent theory and observations. These simulations consist of five LMC-mass galaxies and six Milky Way-mass progenitors (with a minimum baryonic particle mass of $m_{b.min} = 7100 M_{\odot}$), for which we calculate the local mass and energy loading factors on 750~pc scales from the identified outflows. We also characterize the multiphase morphology and properties of the identified superbubbles, including the `shell' of cool ($T<10^5$ K) gas and break out of energetic hot ($T>10^5$ K) gas when the shell bursts. For all galaxies, the outflow mass, momentum, and energy fluxes appear to reach their peak during the identified superbubbles, and we investigate the effects on the interstellar medium (ISM), circumgalactic medium (CGM), and subsequent star formation rates. We find that these simulations, regardless of redshift, have mass-loading factors and momentum fluxes in the cool gas that largely agree with recent observations. Lastly, we also investigate how methodological choices in measuring outflows can affect loading factors for galactic winds.