ACORN I. Massive Black Hole Seeding and Tidal Disruption Events from Star Clusters in Cosmological Simulations
Abstract
JWST has revealed massive star clusters at z≳ 6, which provide promising environments for massive black hole (MBH) seed formation. We introduce a new MBH seeding model for cosmological simulations, physically motivated by the runaway collisions in star clusters. Subgrid star clusters are generated according to the local ISM and evolved through stellar evolution and two-body relaxation. The masses of MBH seeds formed through runaway collisions are determined by the properties of their host clusters, including the effects of metallicity-dependent stellar winds. We further follow tidal disruption events (TDEs) with the evolving clusters, which can be enhanced in MBH binaries, and account for gravitational-wave (GW) recoil following MBH mergers. We implement this model in a constrained simulation of a 5σ overdense region, where seeds of 103−105.6 M⊙ form in clusters with 104≤ mSC≤ 108 M⊙. Because both the seed abundance and mass are directly connected to the local environment, we have a more physical MBH − Mgalaxy scaling for low-mass galaxies (Mgalaxy∼106−9 M⊙), a regime poorly described by previous seeding models. Multiple MBHs are naturally allowed to form in-situ within individual halos, producing a spatially clustered population. This increases the MBH merger rate by ∼100 relative to other seeding models, significantly enhancing the expected LISA event rate. TDEs can dominate the growth of 103−4 M⊙ MBHs and produce luminous flares of Lpeak∼ 1042−43 erg s−1, increasing the observability of low-mass seeds. This seeding prescription accelerates early MBH growth at z≳ 8, while subsequent self-regulated gas accretion drives the central MBH toward similar masses ∼108.6 M⊙ by z=6 across different seeding models.
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BibTeX
@misc{zhou2026acorn,
title = {{ACORN I. Massive Black Hole Seeding and Tidal Disruption Events from Star Clusters in Cosmological Simulations}},
author = {Yihao Zhou and Tiziana Di Matteo and Claire E. Williams and Aklant Kumar Bhowmick and Marta Reina-Campos and Carl L. Rodriguez and Elena González Prieto and Laura Blecha and Rupert Croft},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.12398},
eprint = {2610.12398},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.12398},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - ACORN I. Massive Black Hole Seeding and Tidal Disruption Events from Star Clusters in Cosmological Simulations
AU - Yihao Zhou
AU - Tiziana Di Matteo
AU - Claire E. Williams
AU - Aklant Kumar Bhowmick
AU - Marta Reina-Campos
AU - Carl L. Rodriguez
AU - Elena González Prieto
AU - Laura Blecha
AU - Rupert Croft
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.12398
UR - https://arxiv.org/abs/2610.12398
AB - JWST has revealed massive star clusters at z≳ 6, which provide promising environments for massive black hole (MBH) seed formation. We introduce a new MBH seeding model for cosmological simulations, physically motivated by the runaway collisions in star clusters. Subgrid star clusters are generated according to the local ISM and evolved through stellar evolution and two-body relaxation. The masses of MBH seeds formed through runaway collisions are determined by the properties of their host clusters, including the effects of metallicity-dependent stellar winds. We further follow tidal disruption events (TDEs) with the evolving clusters, which can be enhanced in MBH binaries, and account for gravitational-wave (GW) recoil following MBH mergers. We implement this model in a constrained simulation of a 5σ overdense region, where seeds of 10^3−10^5.6 M_⊙ form in clusters with 10^4≤ m_SC≤ 10^8 M_⊙. Because both the seed abundance and mass are directly connected to the local environment, we have a more physical M_BH − M_galaxy scaling for low-mass galaxies (M_galaxy∼10^6−9 M_⊙), a regime poorly described by previous seeding models. Multiple MBHs are naturally allowed to form in-situ within individual halos, producing a spatially clustered population. This increases the MBH merger rate by ∼100 relative to other seeding models, significantly enhancing the expected LISA event rate. TDEs can dominate the growth of 10^3−4 M_⊙ MBHs and produce luminous flares of L_peak∼ 10^42−43 erg s^−1, increasing the observability of low-mass seeds. This seeding prescription accelerates early MBH growth at z≳ 8, while subsequent self-regulated gas accretion drives the central MBH toward similar masses ∼10^8.6 M_⊙ by z=6 across different seeding models.
ER -