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Chemical Gardens as Flow-through Reactors Simulating Natural Hydrothermal Systems

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Hot bubbles from active galactic nuclei as a heat source in cooling-flow clusters.

Marcus Brüggen¹, Christian R Kaiser

¹International University Bremen, Campus Ring 1, 28759 Bremen, Germany. m.brueggen@iu-bremen.de

|July 19, 2002

Summary

Active galactic nuclei in galaxy clusters inflate buoyant bubbles. These bubbles stir hot gas, increasing cooling times and reducing cold gas deposition, contrary to previous cooling flow models.

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Area of Science:

Astrophysics
Cosmology
Plasma Physics

Background:

Galaxy clusters contain hot, X-ray-emitting plasma.
Observed central X-ray brightness peaks suggest gas cooling flows.
Discrepancies exist between predicted and observed cool gas, implying lower mass deposition rates.

Purpose of the Study:

Investigate the impact of active galactic nuclei (AGN) on gas cooling in galaxy clusters.
Re-evaluate the cooling flow model in light of AGN activity.
Quantify the effect of buoyant bubbles on gas thermodynamics.

Main Methods:

Highly resolved hydrodynamic simulations.
Modeling AGN-inflated plasma bubbles.
Analyzing gas entropy and cooling times in simulated cluster cores.

Main Results:

Buoyant bubbles rise through the cluster atmosphere, stirring the gas.
Simulations show increased cooling times in inner cluster regions.
Significant reduction in cold gas deposition due to bubble activity.

Conclusions:

AGN-driven buoyant bubbles play a crucial role in regulating gas cooling in galaxy clusters.
The cooling flow model may be incomplete without considering AGN feedback.
These findings reconcile discrepancies in observed cool gas amounts.