Stellar Collisions from Self-consistent Stellar Dynamics Around Growing Supermassive black Holes
Abstract
The centers of galaxies harbor the densest stellar environments, where a massive black hole (MBH) accelerates stars to such high velocities that direct collisions can result in high-energetic phenomena, such as gravitational wave sources, kilonovae, and supernova-like transients. These collisions can reshape the cluster's density profile and release gas that can be subsequently accreted by the MBH. However, the evolving rates of such phenomena from self-consistent dynamics around mass-growing MBHs remain largely unexplored. In this work, we simulate nuclear star clusters (NSCs) across a range of masses and density profiles by employing the GNC Monte Carlo code, that self-consistently models stellar dynamics and the subsequent accretion of released gas. We find that stellar collisions flatten the density cusp in the innermost regions (r ≲ 10−3−10−2 pc) within ∼ 0.1−1 Gyr. While high initial collision rates in steep cusps quickly decline due to stellar depletion, the interplay between collisions and MBH growth is important only in massive NSCs (M⋆ ∼ 109 M⊙). As MBH grows, increased stellar velocities shift the balance toward destructive collisions of which relative velocities can be ≳ 2500 km s−1. Consequently, present-day destructive collision rates in massive clusters remain high (10−4∼ 10−3yr−1), whereas they are smaller in Milky Way-like NSCs or negligible in smaller NSCs. Our results highlight a crucial synergy between stellar dynamics and MBH growth, identifying massive galaxies as prime targets for observing transients from destructive stellar collisions.
Related
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BibTeX
@misc{zhang2026stellar,
title = {{Stellar Collisions from Self-consistent Stellar Dynamics Around Growing Supermassive black Holes}},
author = {Fupeng Zhang and Pau Amaro Seoane},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.29136},
eprint = {2609.29136},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.29136},
}
RIS
TY - UNPB
TI - Stellar Collisions from Self-consistent Stellar Dynamics Around Growing Supermassive black Holes
AU - Fupeng Zhang
AU - Pau Amaro Seoane
PY - 2026
DA - 2026/09/24
PB - arXiv
DO - 10.48550/arxiv.2609.29136
UR - https://arxiv.org/abs/2609.29136
AB - The centers of galaxies harbor the densest stellar environments, where a massive black hole (MBH) accelerates stars to such high velocities that direct collisions can result in high-energetic phenomena, such as gravitational wave sources, kilonovae, and supernova-like transients. These collisions can reshape the cluster's density profile and release gas that can be subsequently accreted by the MBH. However, the evolving rates of such phenomena from self-consistent dynamics around mass-growing MBHs remain largely unexplored. In this work, we simulate nuclear star clusters (NSCs) across a range of masses and density profiles by employing the GNC Monte Carlo code, that self-consistently models stellar dynamics and the subsequent accretion of released gas. We find that stellar collisions flatten the density cusp in the innermost regions (r ≲ 10^−3−10^−2 pc) within ∼ 0.1−1 Gyr. While high initial collision rates in steep cusps quickly decline due to stellar depletion, the interplay between collisions and MBH growth is important only in massive NSCs (M_⋆ ∼ 10^9 M_⊙). As MBH grows, increased stellar velocities shift the balance toward destructive collisions of which relative velocities can be ≳ 2500 km s^−1. Consequently, present-day destructive collision rates in massive clusters remain high (10^−4∼ 10^−3yr^−1), whereas they are smaller in Milky Way-like NSCs or negligible in smaller NSCs. Our results highlight a crucial synergy between stellar dynamics and MBH growth, identifying massive galaxies as prime targets for observing transients from destructive stellar collisions.
ER -