Abstract
The interstellar medium is a multiphase gas in which turbulent support is as important as thermal pressure. Sustaining this configuration requires both continuous turbulent stirring and continuous radiative cooling to match the decay of turbulent energy. While this equilibrium can persist for small turbulent velocities, if the one-dimensional velocity dispersion is larger than ≈35 km s-1, the gas moves into an unstable regime that leads to rapid heating. I study the implications of this turbulent runaway, showing that it causes a hot gas outflow to form in all galaxies with a gas surface density above ≈50 M pc-2, corresponding to a star formation rate per unit area of ≈0.1 M yr-1 kpc-2. For galaxies with v esc ≳ 200 km s-1, the sonic point of this hot outflow should lie interior to the region containing cold gas and stars, while for galaxies with smaller escape velocities, the sonic point should lie outside this region. This leads to efficient cold cloud acceleration in higher mass galaxies, while in lower mass galaxies, clouds may be ejected by random turbulent motions rather than accelerated by the wind. Finally, I show that energy balance cannot be achieved at all for turbulent media above a surface density of ≈105 M pc-2.
| Original language | English (US) |
|---|---|
| Article number | L31 |
| Journal | Astrophysical Journal Letters |
| Volume | 763 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 1 2013 |
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Keywords
- galaxies: starburst
- ISM: jets and outflows
- ISM: structure
ASJC Scopus subject areas
- Space and Planetary Science
- Astronomy and Astrophysics
Cite this
Understanding galaxy outflows as the product of unstable turbulent support. / Scannapieco, Evan.
In: Astrophysical Journal Letters, Vol. 763, No. 2, L31, 01.02.2013.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Understanding galaxy outflows as the product of unstable turbulent support
AU - Scannapieco, Evan
PY - 2013/2/1
Y1 - 2013/2/1
N2 - The interstellar medium is a multiphase gas in which turbulent support is as important as thermal pressure. Sustaining this configuration requires both continuous turbulent stirring and continuous radiative cooling to match the decay of turbulent energy. While this equilibrium can persist for small turbulent velocities, if the one-dimensional velocity dispersion is larger than ≈35 km s-1, the gas moves into an unstable regime that leads to rapid heating. I study the implications of this turbulent runaway, showing that it causes a hot gas outflow to form in all galaxies with a gas surface density above ≈50 M pc-2, corresponding to a star formation rate per unit area of ≈0.1 M yr-1 kpc-2. For galaxies with v esc ≳ 200 km s-1, the sonic point of this hot outflow should lie interior to the region containing cold gas and stars, while for galaxies with smaller escape velocities, the sonic point should lie outside this region. This leads to efficient cold cloud acceleration in higher mass galaxies, while in lower mass galaxies, clouds may be ejected by random turbulent motions rather than accelerated by the wind. Finally, I show that energy balance cannot be achieved at all for turbulent media above a surface density of ≈105 M pc-2.
AB - The interstellar medium is a multiphase gas in which turbulent support is as important as thermal pressure. Sustaining this configuration requires both continuous turbulent stirring and continuous radiative cooling to match the decay of turbulent energy. While this equilibrium can persist for small turbulent velocities, if the one-dimensional velocity dispersion is larger than ≈35 km s-1, the gas moves into an unstable regime that leads to rapid heating. I study the implications of this turbulent runaway, showing that it causes a hot gas outflow to form in all galaxies with a gas surface density above ≈50 M pc-2, corresponding to a star formation rate per unit area of ≈0.1 M yr-1 kpc-2. For galaxies with v esc ≳ 200 km s-1, the sonic point of this hot outflow should lie interior to the region containing cold gas and stars, while for galaxies with smaller escape velocities, the sonic point should lie outside this region. This leads to efficient cold cloud acceleration in higher mass galaxies, while in lower mass galaxies, clouds may be ejected by random turbulent motions rather than accelerated by the wind. Finally, I show that energy balance cannot be achieved at all for turbulent media above a surface density of ≈105 M pc-2.
KW - galaxies: starburst
KW - ISM: jets and outflows
KW - ISM: structure
UR - http://www.scopus.com/inward/record.url?scp=84873369684&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84873369684&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/763/2/L31
DO - 10.1088/2041-8205/763/2/L31
M3 - Article
AN - SCOPUS:84873369684
VL - 763
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - L31
ER -