Conduction and the Star-Formation Threshold in Brightest Cluster Galaxies

TL;DR

This paper proposes that electron thermal conduction governs the star-formation threshold in brightest cluster galaxies by mediating AGN feedback effects on the intracluster medium, explaining observed entropy limits.

Contribution

It introduces a conduction-based model for the star-formation threshold in brightest cluster galaxies, linking thermal physics to galaxy evolution.

Findings

Star formation occurs only when intracluster gas entropy is below 30 keV cm^2.

Electron thermal conduction influences AGN feedback and star formation suppression.

The conduction physics sets a critical entropy threshold for star formation in galaxy centers.

Abstract

Current models of galaxy evolution suggest that feedback from active galactic nuclei is needed to explain the high-luminosity cutoff in the galaxy luminosity function. Exactly how an AGN outflow couples with the ambient medium and suppresses star formation remains poorly understood. However, we have recently uncovered an important clue to how that coupling might work. Observations of H-alpha emission and blue light from the universe's most luminous galaxies, which occupy the centers of galaxy clusters, show that star formation happens only if the minimum specific entropy of the intracluster gas is less than 30 keV cm^2. Here we suggest that this threshold for star formation is set by the physics of electron thermal conduction, implying that conduction is critical for channeling AGN energy input toward incipient star-forming regions and limiting the progress of star formation.