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Updated: Jul 19, 2026
06:29
Simulation of Early Earth Hydrothermal Chimneys in a Thermal Gradient Environment
Published on: February 27, 2021
H3+ cooling in primordial gas.
Simon Glover1, Daniel Wolf Savin
1Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany. sglover@aip.de
Summary
Hydrogen molecule (H2) cooling is usually assumed dominant in primordial gas. However, this study shows that hydrogen ion (H3+) cooling can become significant in primordial gas, especially with a strong ionizing background.
Area of Science:
- Cosmology
- Astrochemistry
- Plasma Physics
Background:
- Primordial gas cooling is crucial for structure formation simulations.
- Hydrogen molecule (H2) is typically considered the primary coolant.
- H2 cooling becomes inefficient at high densities due to thermodynamic limitations.
Purpose of the Study:
- To investigate the cooling contribution of other molecules and ions in primordial gas.
- To assess the role of hydrogen ion (H3+) as a high-density coolant.
- To quantify H3+ cooling in simulations of collapsing primordial gas.
Main Methods:
- Simulations of thermal and chemical evolution of primordial gas.
- Detailed treatment of H3+ chemistry.
- Approximate treatment of H3+ cooling.
Main Results:
- H3+ cooling contribution is generally small in most simulated scenarios.
- H3+ cooling can become significant under specific conditions.
- A sufficiently strong ionizing background enhances the importance of H3+ cooling.
Conclusions:
- H2 is not always the dominant coolant in high-density primordial gas.
- H3+ plays a potentially significant role in cooling under ionizing radiation.
- Future simulations should consider H3+ cooling, especially in environments with strong UV backgrounds.
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