The Structure and Composition of Multiphase Galactic Winds in a Large Magellanic Cloud Mass Simulated Galaxy

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 ∼10 ^11 M _⊙ (similar to the Large Magellanic Cloud) and a total gas mass of ∼6 × 10 ^8 M _⊙ , resulting in ∼10 ^8 gas cells at ∼4 M _⊙ mass resolution. We adopt a resolved stellar feedback model with nonequilibrium cooling and heating, including photoelectric heating and photoionizing radiation, as well as supernovae, coupled to the second-order meshless finite-mass method for hydrodynamics. These features make this the largest resolved interstellar medium (ISM) galaxy model run to date. We find mean star formation rates around 0.05 M _⊙ yr ^−1 and evaluate typical time-averaged loading factors for mass ( η _M ∼ 1.0, in good agreement with recent observations) and energy ( η _E ∼ 0.01). The bulk of the mass of the wind is transported by the warm ( T 5 × 10 ^5 K). We find an average opening angle of 30° 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 Σ _SFR , while the energy loading shows inverted trends with Σ _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 multiphase ISM.

Keywords

• Galactic winds
• Galaxy evolution
• Hydrodynamical simulations
• Stellar feedback
• Interstellar medium