A new clump-based star formation model for galaxy simulations: implications for high-redshift compact star clusters
Abstract
We develop a new star formation model for galaxy simulations in which star-forming gas clumps are identified on-the-fly and converted into stars with an efficiency εSF set by the clump surface density Σc, calibrated against radiation hydrodynamics simulations of star cluster formation. Applying this model to isolated disc galaxies embedded in haloes of Mh=109, 1010 and 1011 M⊙, with disc compactness corresponding to redshift z=0--$10$, we find that more compact discs form more massive and denser clumps. The maximum clump mass increases from ∼ 105 to ∼ 107 M⊙, and the fraction of clumps exceeding the surface density of 300 M⊙ pc−2 rises from $0.25$ to $0.38$ between z=0 and $10$ in 1010 M⊙ haloes. Star formation becomes correspondingly bursty, and the global star formation efficiency after three disc rotations increases from 5 × 10−3 to 2 × 10−1 in 1010 M⊙ haloes and from 2 × 10−2 to 4 × 10−1 in 1011 M⊙ haloes as the redshift increases from z=0 to $10$. The accompanying feedback disrupts the gas discs of the most compact systems, while prominent stellar spiral arms emerge. Self-gravitationally bound star clusters form only in compact discs. We find no bound star clusters at z ≤ 2 in 1010 M⊙ haloes, whereas the bound cluster mass fraction reaches ≈ 40 per cent at z ≥ 8 and ≈ 70 per cent in the most compact 1011 M⊙ halo. These fractions are broadly consistent with those inferred for high-z clumpy galaxies observed by the James Webb Space Telescope.
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BibTeX
@misc{horie2026clumpbased,
title = {{A new clump-based star formation model for galaxy simulations: implications for high-redshift compact star clusters}},
author = {Shu Horie and Hidenobu Yajima},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.07635},
eprint = {2609.07635},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07635},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A new clump-based star formation model for galaxy simulations: implications for high-redshift compact star clusters
AU - Shu Horie
AU - Hidenobu Yajima
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.07635
UR - https://arxiv.org/abs/2609.07635
AB - We develop a new star formation model for galaxy simulations in which star-forming gas clumps are identified on-the-fly and converted into stars with an efficiency ε_SF set by the clump surface density Σ_c, calibrated against radiation hydrodynamics simulations of star cluster formation. Applying this model to isolated disc galaxies embedded in haloes of M_h=10^9, 10^10 and 10^11 M_⊙, with disc compactness corresponding to redshift z=0--$10$, we find that more compact discs form more massive and denser clumps. The maximum clump mass increases from ∼ 10^5 to ∼ 10^7 M_⊙, and the fraction of clumps exceeding the surface density of 300 M_⊙ pc^−2 rises from $0.25$ to $0.38$ between z=0 and $10$ in 10^10 M_⊙ haloes. Star formation becomes correspondingly bursty, and the global star formation efficiency after three disc rotations increases from 5 × 10^−3 to 2 × 10^−1 in 10^10 M_⊙ haloes and from 2 × 10^−2 to 4 × 10^−1 in 10^11 M_⊙ haloes as the redshift increases from z=0 to $10$. The accompanying feedback disrupts the gas discs of the most compact systems, while prominent stellar spiral arms emerge. Self-gravitationally bound star clusters form only in compact discs. We find no bound star clusters at z ≤ 2 in 10^10 M_⊙ haloes, whereas the bound cluster mass fraction reaches ≈ 40 per cent at z ≥ 8 and ≈ 70 per cent in the most compact 10^11 M_⊙ halo. These fractions are broadly consistent with those inferred for high-z clumpy galaxies observed by the James Webb Space Telescope.
ER -