How does a galaxy's quenching probability depend on its black hole's mass?
Abstract
We develop a parametric toy model to explore how black hole mass scatter σBH and the dependence of the quenching probability per unit time on black hole mass, parameterized as a power law with index q, jointly control the faint-end slope α of the stellar mass function of quenched central galaxies. By varying σBH and q, we identify two regimes. At low scatter, σBH ≲ 0.4 dex, α is strongly sensitive to q. Gradual quenching, represented by low q, produces shallow slopes, while sharp thresholds, with high q, produce steep mass functions, making α a powerful diagnostic of AGN feedback prescriptions. At large scatter, σBH ≳ 0.6 dex, models with vastly different q converge to similar quenched mass functions, because the intrinsic scatter erases the imprint of the feedback implementation. Comparing to cosmological hydrodynamical simulations and semianalytic models, only models with σBH ≳ 0.4 dex match the observed faint-end slope of α≈ 0.7. {\sc SAGE}, {\sc Dark Sage}, and {\sc COLIBRE}, with σBH of 2.0, 0.6, and 0.4 dex, respectively, reproduce this slope, whereas {\sc IllustrisTNG} and {\sc EAGLE}, with σBH ≲ 0.2 dex, produce steeper slopes. Current observational estimates of σBH allow a wide range of q ≳ 0.8, so the observed slope alone cannot identify the quenching prescription. If σBH is small, simultaneous measurements of α and σBH can distinguish between competing AGN feedback models.
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BibTeX
@misc{porrasvalverde2026does,
title = {{How does a galaxy's quenching probability depend on its black hole's mass?}},
author = {Antonio J. Porras-Valverde and John C. Forbes},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.27061},
eprint = {2610.27061},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.27061},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - How does a galaxy's quenching probability depend on its black hole's mass?
AU - Antonio J. Porras-Valverde
AU - John C. Forbes
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.27061
UR - https://arxiv.org/abs/2610.27061
AB - We develop a parametric toy model to explore how black hole mass scatter σ_BH and the dependence of the quenching probability per unit time on black hole mass, parameterized as a power law with index q, jointly control the faint-end slope α of the stellar mass function of quenched central galaxies. By varying σ_BH and q, we identify two regimes. At low scatter, σ_BH ≲ 0.4 dex, α is strongly sensitive to q. Gradual quenching, represented by low q, produces shallow slopes, while sharp thresholds, with high q, produce steep mass functions, making α a powerful diagnostic of AGN feedback prescriptions. At large scatter, σ_BH ≳ 0.6 dex, models with vastly different q converge to similar quenched mass functions, because the intrinsic scatter erases the imprint of the feedback implementation. Comparing to cosmological hydrodynamical simulations and semianalytic models, only models with σ_BH ≳ 0.4 dex match the observed faint-end slope of α≈ 0.7. {\sc SAGE}, {\sc Dark Sage}, and {\sc COLIBRE}, with σ_BH of 2.0, 0.6, and 0.4 dex, respectively, reproduce this slope, whereas {\sc IllustrisTNG} and {\sc EAGLE}, with σ_BH ≲ 0.2 dex, produce steeper slopes. Current observational estimates of σ_BH allow a wide range of q ≳ 0.8, so the observed slope alone cannot identify the quenching prescription. If σ_BH is small, simultaneous measurements of α and σ_BH can distinguish between competing AGN feedback models.
ER -