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Peer-reviewedCC BY 4.0The Astrophysical Journal

Black Hole Occupation Fraction: Dependence on Black Hole Mass Threshold, Environment, Resolution, and Redshift

  • Emanuele Contini1
  • J. K. Jang1
  • Jinsu Rhee2
  • Changjo Seo1
  • Sukyoung K. Yi1
  1. 1Yonsei University
  2. 2Sorbonne Université
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Abstract

We take advantage of the state-of-the-art semianalytic model FEGA25 , 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. FEGA25 includes an improved treatment of active galactic nucleus (AGN) feedback and does not impose a preexisting BH seed population: BHs grow naturally through quasar and radio modes. Starting from the prerequisite that 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 NewCluster zoom-in simulation show a trend qualitatively similar to that reported by M. Tremmel et al., 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.

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Cite

BibTeXRIS
BibTeX
@article{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},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/aeab8c},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeab8c},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
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  - 2026/10/28
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aeab8c
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aeab8c
AB  - We take advantage of the state-of-the-art semianalytic model FEGA25 , 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. FEGA25 includes an improved treatment of active galactic nucleus (AGN) feedback and does not impose a preexisting BH seed population: BHs grow naturally through quasar and radio modes. Starting from the prerequisite that 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 NewCluster zoom-in simulation show a trend qualitatively similar to that reported by M. Tremmel et al., 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.
SN  - 1538-4357
SN  - 0004-637X
ER  -