IDENTIFICATION OF A FUNDAMENTAL TRANSITION IN A TURBULENTLY SUPPORTED INTERSTELLAR MEDIUM
- School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States)
The interstellar medium (ISM) in star-forming galaxies is a multiphase gas in which turbulent support is at least as important as thermal pressure. Sustaining this configuration requires continuous radiative cooling, such that the overall average cooling rate matches the decay rate of turbulent energy into the medium. Here we carry out a set of numerical simulations of a stratified, turbulently stirred, radiatively cooled medium, which uncover a fundamental transition at a critical one-dimensional turbulent velocity of Almost-Equal-To 35 km s{sup -1}. At turbulent velocities below Almost-Equal-To 35 km s{sup -1}, corresponding to temperatures below 10{sup 5.5} K, the medium is stable, as the time for gas to cool is roughly constant as a function of temperature. On the other hand, at turbulent velocities above the critical value, the gas is shocked into an unstable regime in which the cooling time increases strongly with temperature, meaning that a substantial fraction of the ISM is unable to cool on a turbulent dissipation timescale. This naturally leads to runaway heating and ejection of gas from any stratified medium with a 1D turbulent velocity above Almost-Equal-To 35 km s{sup -1}, a result that has implications for galaxy evolution at all redshifts.
- OSTI ID:
- 22011816
- Journal Information:
- Astrophysical Journal, Vol. 746, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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