Energy deposited by black holes in the hot X-ray gas of elliptical galaxies, groups and clusters
Abstract
Galaxy groups show entropy excesses ΔS with respect to theoretical expectations from models and simulations with purely gravitational heating. We determine the heat Qheat≃ TΔS 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 ΔS=S−S0 by taking the difference between S and the entropy S0 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 M200>1014 M⊙), heating and cooling are in self-regulated equilibrium.
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BibTeX
@misc{cattaneo2026energy,
title = {{Energy deposited by black holes in the hot X-ray gas of elliptical galaxies, groups and clusters}},
author = {A Cattaneo and S Ettori},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.01407},
eprint = {2609.01407},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05758431v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Energy deposited by black holes in the hot X-ray gas of elliptical galaxies, groups and clusters
AU - A Cattaneo
AU - S Ettori
PY - 2026
DA - 2026/09/04
PB - HAL
DO - 10.48550/arxiv.2609.01407
UR - https://hal.science/hal-05758431v1
AB - Galaxy groups show entropy excesses ΔS with respect to theoretical expectations from models and simulations with purely gravitational heating. We determine the heat Q_heat≃ TΔS 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 ΔS=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 M_⊙), heating and cooling are in self-regulated equilibrium.
ER -