INFERNO: Galactic winds in dwarf galaxies with star-by-star simulations including runaway stars

TL;DR

This paper introduces INFERNO, a novel galaxy simulation model that incorporates star-by-star feedback, including runaway stars, to study galactic winds in dwarf galaxies, revealing complex multi-phase outflows and minimal impact of runaway stars.

Contribution

INFERNO is the first hydrodynamic simulation model to include resolved stellar objects with star-by-star feedback and kinematics, applied specifically to dwarf galaxies.

Findings

Galactic winds in dwarf galaxies are vigorous with high mass and metal loading factors.

Outflows are multi-phase, spanning nearly 8 orders of magnitude in temperature.

Runaway stars have little impact on feedback outcomes in dwarf galaxies due to strong feedback and porous ISM.

Abstract

The formation and evolution of galaxies have proved sensitive to the inclusion of stellar feedback, which is therefore crucial to any successful galaxy model. We present INFERNO, a new model for hydrodynamic simulations of galaxies, which incorporates resolved stellar objects with star-by-star calculations of when and where the injection of enriched material, momentum, and energy takes place. INFERNO treats early stellar kinematics to include phenomena such as walkaway and runaway stars. We employ this innovative model on simulations of a dwarf galaxy and demonstrate that our physically motivated stellar feedback model can drive vigorous galactic winds. This is quantified by mass and metal loading factors in the range of $10-100$, and an energy loading factor close to unity. Outflows are established close to the disc, are highly multi-phase, spanning almost $8$ orders of magnitude in temperature, and with a clear dichotomy between mass ejected in cold, slow-moving ($T\lesssim5\times10^4\,{\rm K}$, $v<100\,{\rm km\,s}^{-1}$) gas and energy ejected in hot, fast-moving ($T>10^6\,{\rm K}$, $v>100\,{\rm km\,s}^{-1}$) gas. In contrast to massive disc galaxies, we find a surprisingly weak impact of the early stellar kinematics, with runaway stars having little to no effect on our results, despite exploding in diffuse gas outside the dense star-forming gas, as well as outside the galactic disc entirely. We demonstrate that this weak impact in dwarf galaxies stems from a combination of strong feedback and a porous interstellar medium, which obscure any unique signatures that runaway stars provide.