Quantifying Supernovae-driven Multiphase Galactic Outflows

• Published in: The Astrophysical journal 2017-06, Vol.841 (2), p.101
• Main Authors: Li, Miao, Bryan, Greg L., Ostriker, Jeremiah P.
• Format: Article
• Language: English
• Subjects: Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; DENSITY; Disk galaxies; DISTRIBUTION; EFFICIENCY; GALACTIC EVOLUTION; GALAXIES; galaxies: formation; galaxies: ISM; GRAVITATIONAL FIELDS; HYDRODYNAMICS; ISM: kinematics and dynamics; ISM: structure; MASS; METALS; Outflow; Photoelectricity; RESOLUTION; Scale height; Star & galaxy formation; Star formation; SUPERNOVAE; SURFACES; Vertical distribution
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa7263

Galactic outflows are observed everywhere in star-forming disk galaxies and are critical for galaxy formation. Supernovae (SNe) play the key role in driving the outflows, but there is no consensus as to how much energy, mass, and metal they can launch out of the disk. We perform 3D, high-resolution hydrodynamic simulations to study SNe-driven outflows from stratified media. Assuming the SN rate scales with gas surface density gas as in the Kennicutt-Schmidt relation, we find that the mass loading factor, m, defined as the mass outflow flux divided by the star formation surface density, decreases with increasing gas as . Approximately gas 50 M pc−2 marks when m 1. About 10%-50% of the energy and 40%-80% of the metals produced by SNe end up in the outflows. The tenuous hot phase (T > 3 × 105 K), which fills 60%-80% of the volume at the midplane, carries the majority of the energy and metals in the outflows. We discuss how various physical processes, including the vertical distribution of SNe, photoelectric heating, external gravitational field, and SN rate, affect the loading efficiencies. The relative scale height of gas and SNe is a very important factor in determining the loading efficiencies.