Black Hole Occupation Fraction: Dependence on Black Hole Mass Threshold, Environment, Resolution and Redshift
Abstract
We take advantage of the state-of-the-art semi-analytic model \texttt{FEGA25} \citep{contini2025}, run on merger trees extracted from three dark matter-only cosmological simulations, to study the relation between the black hole (BH) occupation fraction, fBH,occ, and galaxy stellar mass as a function of BH mass threshold, galaxy type, simulated volume, numerical resolution, sampled galaxy population, and redshift. \texttt{FEGA25} includes an improved treatment of active galactic nucleus feedback and does not impose a pre-existing BH seed population: BHs grow naturally through quasar and radio modes. Starting from the prerequisite that \texttt{FEGA25} reproduces the observed BH mass function from at least z=2 to the present day, our analysis leads to several results. We find that fBH,occ increases with stellar mass, but that its normalization and shape depend strongly on the adopted BH mass threshold and on the relative contribution of central and satellite galaxies. The relative behavior of central and satellite galaxies depends on the simulation box and BH mass threshold, while the global relation should be interpreted as a population-weighted quantity. We also find significant box-to-box variations, reflecting the combined impact of numerical resolution, simulated volume, and sampled galaxy population. The redshift evolution is not universal: YS50 and the \texttt{NewCluster} zoom-in simulation show a trend qualitatively similar to that reported by \citet{tremmel2024}, whereas larger-volume boxes show the opposite behavior. Finally, comparison with other studies shows that the inferred occupation fraction is highly sensitive to BH mass threshold, simulated volume, numerical resolution, and sampled galaxy population.
Related
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- The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation
BibTeX
@misc{contini2026black,
title = {{Black Hole Occupation Fraction: Dependence on Black Hole Mass Threshold, Environment, Resolution and Redshift}},
author = {Emanuele Contini and J. K. Jang and Jinsu Rhee and Changjo Seo and Sukyoung K. Yi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.22758},
eprint = {2606.22758},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.22758},
note = {CC0},
}
RIS
TY - UNPB
TI - Black Hole Occupation Fraction: Dependence on Black Hole Mass Threshold, Environment, Resolution and Redshift
AU - Emanuele Contini
AU - J. K. Jang
AU - Jinsu Rhee
AU - Changjo Seo
AU - Sukyoung K. Yi
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2606.22758
UR - https://arxiv.org/abs/2606.22758
AB - We take advantage of the state-of-the-art semi-analytic model \texttt{FEGA25} \citep{contini2025}, run on merger trees extracted from three dark matter-only cosmological simulations, to study the relation between the black hole (BH) occupation fraction, f_BH,occ, and galaxy stellar mass as a function of BH mass threshold, galaxy type, simulated volume, numerical resolution, sampled galaxy population, and redshift. \texttt{FEGA25} includes an improved treatment of active galactic nucleus feedback and does not impose a pre-existing BH seed population: BHs grow naturally through quasar and radio modes. Starting from the prerequisite that \texttt{FEGA25} reproduces the observed BH mass function from at least z=2 to the present day, our analysis leads to several results. We find that f_BH,occ increases with stellar mass, but that its normalization and shape depend strongly on the adopted BH mass threshold and on the relative contribution of central and satellite galaxies. The relative behavior of central and satellite galaxies depends on the simulation box and BH mass threshold, while the global relation should be interpreted as a population-weighted quantity. We also find significant box-to-box variations, reflecting the combined impact of numerical resolution, simulated volume, and sampled galaxy population. The redshift evolution is not universal: YS50 and the \texttt{NewCluster} zoom-in simulation show a trend qualitatively similar to that reported by \citet{tremmel2024}, whereas larger-volume boxes show the opposite behavior. Finally, comparison with other studies shows that the inferred occupation fraction is highly sensitive to BH mass threshold, simulated volume, numerical resolution, and sampled galaxy population.
ER -