Galaxy Outflows Without Supernovae
Sharanya Sur, Evan Scannapieco, Eve C. Ostriker

TL;DR
This study shows that high velocity dispersions from gravitational instabilities alone can drive significant galactic outflows in dense, high-redshift disks without requiring supernova feedback, due to a turbulent heating instability.
Contribution
It demonstrates that turbulence from gravitational instabilities can generate outflows in galaxies independently of supernovae, highlighting a new mechanism for galaxy evolution.
Findings
Strong outflows occur in dense disks with velocity dispersions >35 km/s.
Outflows are driven by a thermal runaway from turbulent heating and inefficient cooling.
Diffuse disks show weak or no outflows despite high turbulence.
Abstract
High surface density, rapidly star-forming galaxies are observed to have line-of-sight velocity dispersions, which are much higher than expected from supernova driving alone, but may arise from large-scale gravitational instabilities. Using three-dimensional simulations of local regions of the interstellar medium, we explore the impact of high velocity dispersions that arise from these disk instabilities. Parametrizing disks by their surface densities and epicyclic frequencies, we conduct a series of simulations that probe a broad range of conditions. Turbulence is driven purely horizontally and on large scales, neglecting any energy input from supernovae. We find that such motions lead to strong global outflows in the highly-compact disks that were common at high redshifts, but weak or negligible mass loss in the more diffuse disks that are prevalent…
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