The structure and composition of multiphase galactic winds in a Large Magellanic Cloud mass simulated galaxy

TL;DR

This study uses high-resolution simulations to analyze multiphase galactic winds in a galaxy similar to the Large Magellanic Cloud, revealing detailed wind structure, composition, and scaling relations with star formation activity.

Contribution

It presents the largest resolved-ISM galaxy model to date, incorporating advanced feedback physics and analyzing the multiphase structure and scaling of galactic winds.

Findings

Warm phase dominates wind mass transport.

Energy is similarly carried by warm and hot phases.

Wind opening angle averages 30 degrees.

Abstract

We present the first results from a high resolution simulation with a focus on galactic wind driving for an isolated galaxy with a halo mass of $\sim 10^{11}$ M$_{\odot}$ (similar to the Large Magellanic Cloud) and a total gas mass of $\sim 6 \times 10^{8}$ M$_{\odot}$, resulting in $\sim 10^{8}$ gas cells at $\sim 4$ M$_{\odot}$ mass resolution. We adopt a resolved stellar feedback model with non-equilibrium cooling and heating, including photoelectric heating and photo-ionizing radiation, as well as supernovae (SNe), coupled to the second order meshless finite mass (MFM) method for hydrodynamics. These features make this the largest resolved-ISM galaxy model run to date. We find mean star formation rates around $0.05$ M$_{\odot}$ yr$^{-1}$ and evaluate typical time averaged loading factors for mass ($\eta_\mathrm{M}$ $\sim$ 1.0, in good agreement with recent observations) and energy ($\eta_\mathrm{E}$ $\sim$ 0.01). The bulk of the mass of the wind is transported by the warm ($T < 5 \times 10^5$K) phase, while there is a similar amount of energy transported in the warm and the hot phases ($T > 5 \times 10^5$K). We find an average opening angle of 30 degrees for the wind, decreasing with higher altitude above the midplane. The wind mass loading is decreasing (flat) for the warm (hot) phase as a function of the star formation surface rate density $\Sigma_{\rm SFR}$, while the energy loading shows inverted trends with $\Sigma_{\rm SFR}$, decreasing for the warm wind and increasing for the hot wind, although with very shallow slopes. These scalings are in good agreement with previous simulations of resolved wind driving in the multi-phase ISM.