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This study examines how supermassive black holes at the centers of galaxies inject energy into surrounding hot gas in galaxy groups and clusters. Researchers found that black holes convert approximately 1-3% of their energy output into heat that is absorbed by the gas, which helps explain observed entropy levels that exceed predictions from gravitational heating alone. The analysis reveals two distinct regimes: in smaller systems like elliptical galaxies and groups, black hole heating rapidly exceeds cooling and can shut down star formation, while in massive galaxy clusters, heating and cooling reach a self-regulated balance.
Why it matters
This research provides a quantitative mechanism for understanding how supermassive black holes regulate star formation and gas properties across cosmic scales, offering insights into galaxy evolution and the energy balance in some of the universe's largest structures.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Abstract: Galaxy groups show entropy excesses $Delta S$ with respect to theoretical expectations from models and simulations with purely gravitational heating. We determine the heat $Q_{rm heat}simeq TDelta S$ deposited by non-gravitational sources into the hot gas of elliptical galaxies, groups and clusters, and to compare it with the energy output of their central black holes (BHs). We adopt a simple model for the hot gas with only one free parameter: the core entropy. We calibrate the core entropy on the observed relation between X-ray luminosity and halo mass, and we use it to determine the entropy $S$ of the hot gas. We determine $Delta S=S-S_0$ by taking the difference between $S$ and the entropy $S_0$ found in cosmological adiabatic simulations for haloes of the same mass. The temperature $T$ of the hot gas during the heating phase is determined from semi-analytic/semi-empirical modelling by assuming that heat absorption traces the accretion histories of supermassive BHs. Our findings suggest that supermassive BHs thermalise 1 to $3%$ of their energy output in the surrounding gas. Our results suggest two regimes: (i) in elliptical galaxies and groups, active galactic nuclei (AGN) heat the gas much more rapidly than it can cool, generating the observed entropy excesses and quenching star formation when the accumulated heat is large enough to unbind the gas reservoir in the host halo; (ii) in galaxy clusters (at $M_{200}>10^{14}{rm,M}_odot$), heating and cooling are in self-regulated equilibrium.
Source: Energy deposited by black holes in the hot X-ray gas of elliptical galaxies, groups and clusters