Production of Cool Gas in Thermally Driven Outflows

Galactic outflows commonly contain multiphase gas, and its physical origin requires explanation. Using the Cholla Galactic OutfLow Simulations suite of high-resolution isolated galaxy models, we demonstrate the viability of rapid radiative cooling as a source of fast-moving (v ∼ 1000 km s−1), cool (...

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Bibliographic Details
Published in:The Astrophysical journal 2018-07, Vol.862 (1), p.56
Main Authors: Schneider, Evan E., Robertson, Brant E., Thompson, Todd A.
Format: Article
Language:English
Subjects:
Astronomical models
astronomy & astrophysics
ASTRONOMY AND ASTROPHYSICS
Astrophysics
Computer simulation
Cooling
Cooling flows (astrophysics)
Cooling rate
Density
evolution - galaxies
Feedback
formation - galaxies
Galactic halos
Galaxies
galaxies: evolution
galaxies: formation
galaxies: starburst
Gas absorption
Halos
Interstellar gas
Interstellar matter
Interstellar medium
Loading rate
Multiphase
Outflow
Parameter identification
Radiative cooling
Red shift
Star & galaxy formation
Star formation
Star formation rate
starburst
Stellar winds
Viability
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Summary:Galactic outflows commonly contain multiphase gas, and its physical origin requires explanation. Using the Cholla Galactic OutfLow Simulations suite of high-resolution isolated galaxy models, we demonstrate the viability of rapid radiative cooling as a source of fast-moving (v ∼ 1000 km s−1), cool (104 K) gas observed in absorption-line studies of outflows around some star-forming galaxies. By varying the mass loading and geometry of the simulated winds, we identify a region of parameter space that leads to cool gas in outflows. In particular, when using an analytically motivated central feedback model, we find that cooling flows can be produced with reasonable mass-loading rates ( ), provided that the star formation rate surface density is high. When a more realistic clustered feedback model is applied, destruction of high-density clouds near the disk and interactions between different outflow regions indicate that lower mass-loading rates of the hot gas within the feedback region may still produce multiphase outflows. These results suggest an origin for fast-moving cool gas in outflows that does not rely on directly accelerating cool gas from the interstellar medium. These cooling flows may additionally provide an explanation for the multiphase gas ubiquitously observed in the halos of star-forming galaxies at low redshift.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/aacce1