From Cosmological Simulations to Binary Black Hole Mergers: The Impact of Using Analytical Star Formation History Models on Gravitational-wave Source Populations
8 affiliations
- 1University of California
- 2Johns Hopkins University
- 3Radboud University
- 4Polish Academy of Sciences
- 5Universität Heidelberg
- 6Università di Padova
- 7Max Planck Institute for Astrophysics
- 8Columbia University
Abstract
Observations of binary black hole (BBH) mergers provide a unique window into the lives of massive stars across cosmic time. Connecting redshift-dependent merger properties to massive star progenitors requires accurate models of cosmic star formation and chemical enrichment histories. Analytical fits for the metallicity-specific cosmic star formation rate density S ( Z , z ) are commonly used as proxies for the complex underlying star formation history, yet they remain unconstrained. Using the IllustrisTNG cosmological simulations, we evaluate the accuracy of these analytical S ( Z , z ) prescriptions. By coupling the simulated and analytical S ( Z , z ) to the population synthesis code COMPAS , we investigate the resulting BBH merger rates and mass distributions. We find that analytical S ( Z , z ) prescriptions can overestimate BBH merger rates at high redshift ( z ≳ 6) by up to a factor of 10–10 ⁴ , depending on cosmological simulation resolution, and can introduce spurious features in the BBH mass distribution. For example, they can produce an artificial feature near 8 M ⊙ in the primary mass distribution at z ≲ 2, which is absent when using the full simulation-based S ( Z , z ) , while simultaneously suppressing high-mass features. These discrepancies arise because simple analytical models fail to capture a high-metallicity bump and a more flattened low-metallicity tail in the simulated S ( Z , z ) metallicity distribution. Our results highlight the importance of accurate star formation histories for modeling BBH populations, demonstrate the limitation of widely used analytical S ( Z , z ) fits, and underscore the need for careful integration of cosmological simulations, analytical fits, and population synthesis when interpreting gravitational-wave observations.
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BibTeX
@article{levina2026from,
title = {{From Cosmological Simulations to Binary Black Hole Mergers: The Impact of Using Analytical Star Formation History Models on Gravitational-wave Source Populations}},
author = {Sasha Levina and Floor Broekgaarden and Lieke van Son and Emanuele Berti and Amedeo Romagnolo and Ruediger Pakmor and Ana Lam},
journal = {The Astrophysical Journal},
year = {2026},
month = sep,
doi = {10.3847/1538-4357/ae9c2f},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/ae9c2f},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - From Cosmological Simulations to Binary Black Hole Mergers: The Impact of Using Analytical Star Formation History Models on Gravitational-wave Source Populations
AU - Sasha Levina
AU - Floor Broekgaarden
AU - Lieke van Son
AU - Emanuele Berti
AU - Amedeo Romagnolo
AU - Ruediger Pakmor
AU - Ana Lam
PY - 2026
DA - 2026/09/30
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae9c2f
UR - https://iopscience.iop.org/article/10.3847/1538-4357/ae9c2f
AB - Observations of binary black hole (BBH) mergers provide a unique window into the lives of massive stars across cosmic time. Connecting redshift-dependent merger properties to massive star progenitors requires accurate models of cosmic star formation and chemical enrichment histories. Analytical fits for the metallicity-specific cosmic star formation rate density S ( Z , z ) are commonly used as proxies for the complex underlying star formation history, yet they remain unconstrained. Using the IllustrisTNG cosmological simulations, we evaluate the accuracy of these analytical S ( Z , z ) prescriptions. By coupling the simulated and analytical S ( Z , z ) to the population synthesis code COMPAS , we investigate the resulting BBH merger rates and mass distributions. We find that analytical S ( Z , z ) prescriptions can overestimate BBH merger rates at high redshift ( z ≳ 6) by up to a factor of 10–10 ⁴ , depending on cosmological simulation resolution, and can introduce spurious features in the BBH mass distribution. For example, they can produce an artificial feature near 8 M ⊙ in the primary mass distribution at z ≲ 2, which is absent when using the full simulation-based S ( Z , z ) , while simultaneously suppressing high-mass features. These discrepancies arise because simple analytical models fail to capture a high-metallicity bump and a more flattened low-metallicity tail in the simulated S ( Z , z ) metallicity distribution. Our results highlight the importance of accurate star formation histories for modeling BBH populations, demonstrate the limitation of widely used analytical S ( Z , z ) fits, and underscore the need for careful integration of cosmological simulations, analytical fits, and population synthesis when interpreting gravitational-wave observations.
SN - 0004-637X
SN - 1538-4357
ER -