Dynamical pairing in gravitational wave populations
Abstract
Binary black holes formed dynamically in star clusters are often associated with nearly equal-mass pairing. We show that this expectation is incomplete. The more general prediction of dynamical assembly is an ordered-pairing relation in which the two black holes are drawn independently from a common one--body mass spectrum and then ordered by mass. Once the primary-mass distribution is known, this relation fixes the conditional companion distribution p(m2| m1). We validate this picture with cluster simulations. In these models, the ordered-draw relation reproduces the morphology of the mass-pairing distribution, including fixed-m2 ridges that are inherited from the one--body mass spectrum: features at nearly constant secondary mass that extend over a range of primary masses and therefore correspond to decreasing q=m2/m1 as m1 increases. Thus, the geometry of the mass distribution itself becomes a formation-channel diagnostic. Dynamical pairing maps peaks of the primary-mass spectrum into fixed-m2 ridges with predictable amplitude, whereas isolated binary evolution more naturally produces structures at fixed q. Applying this test to a non-parametric reconstruction of the gravitational-wave population, we find a tentative enhancement at m2≃ 30 M⊙ for m1≳ 40 M⊙ that is broadly compatible with ordered pairing. Finally, we show that dynamical formation naturally explains the rapid decline of the secondary-mass distribution above ∼30 M⊙ recently reported by the LIGO--Virgo--KAGRA Collaboration.
Related
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BibTeX
@misc{antonini2026dynamical,
title = {{Dynamical pairing in gravitational wave populations}},
author = {Fabio Antonini and Aleksandra Olejak and Isobel Romero-Shaw and Matthew Mould},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.09834},
eprint = {2610.09834},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.09834},
}
RIS
TY - UNPB
TI - Dynamical pairing in gravitational wave populations
AU - Fabio Antonini
AU - Aleksandra Olejak
AU - Isobel Romero-Shaw
AU - Matthew Mould
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.09834
UR - https://arxiv.org/abs/2610.09834
AB - Binary black holes formed dynamically in star clusters are often associated with nearly equal-mass pairing. We show that this expectation is incomplete. The more general prediction of dynamical assembly is an ordered-pairing relation in which the two black holes are drawn independently from a common one--body mass spectrum and then ordered by mass. Once the primary-mass distribution is known, this relation fixes the conditional companion distribution p(m_2| m_1). We validate this picture with cluster simulations. In these models, the ordered-draw relation reproduces the morphology of the mass-pairing distribution, including fixed-m_2 ridges that are inherited from the one--body mass spectrum: features at nearly constant secondary mass that extend over a range of primary masses and therefore correspond to decreasing q=m_2/m_1 as m_1 increases. Thus, the geometry of the mass distribution itself becomes a formation-channel diagnostic. Dynamical pairing maps peaks of the primary-mass spectrum into fixed-m_2 ridges with predictable amplitude, whereas isolated binary evolution more naturally produces structures at fixed q. Applying this test to a non-parametric reconstruction of the gravitational-wave population, we find a tentative enhancement at m_2≃ 30 M_⊙ for m_1≳ 40 M_⊙ that is broadly compatible with ordered pairing. Finally, we show that dynamical formation naturally explains the rapid decline of the secondary-mass distribution above ∼30 M_⊙ recently reported by the LIGO--Virgo--KAGRA Collaboration.
ER -