A subpopulation of low-mass, spinning black holes: signatures of dynamical assembly

Fuente: arXiv
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Main Authors: Tong, Hui, Callister, Thomas A., Fishbach, Maya, Thrane, Eric, Antonini, Fabio, Stevenson, Simon, Romero-Shaw, Isobel M., Dosopoulou, Fani
Format: Preprint
Published: 2025
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_version_ 1866909892860706816
author Tong, Hui
Callister, Thomas A.
Fishbach, Maya
Thrane, Eric
Antonini, Fabio
Stevenson, Simon
Romero-Shaw, Isobel M.
Dosopoulou, Fani
author_facet Tong, Hui
Callister, Thomas A.
Fishbach, Maya
Thrane, Eric
Antonini, Fabio
Stevenson, Simon
Romero-Shaw, Isobel M.
Dosopoulou, Fani
contents Gravitational-wave observations of massive, rapidly spinning binary black holes mergers provide increasing evidence for the dynamical origin of some mergers. Previous studies have interpreted the mergers with primary mass $\gtrsim45\,M_\odot$ as being dominated by hierarchical, second-generation mergers, with rapidly spinning primaries being the products of previous black hole mergers assembled in dense stellar clusters. In this work, we reveal confident evidence of another subpopulation with rapid and isotropic spins at low mass containing the two exceptional events GW241011 and GW241110, consistent with a hierarchical merger hypothesis. Our result suggests the mass distribution of the second-generation black holes is peaked at low primary masses of $\sim16\,M_\odot$ rather than $\gtrsim45\,M_\odot$ in the pair-instability gap. Such low-mass second-generation black holes must be formed from the merger of even lighter first-generation black holes, implying that dense, metal-rich stellar environments contribute to the binary black hole population. By separating the contamination of higher-generation black holes, our result reveals the primary mass distribution of first-generation black holes formed from stellar collapse, which shows a significant dip between $\sim12\,M_\odot$ to $\sim20\,M_\odot$. This may indicate a dearth of black holes due to variation in the core compactness of the progenitor.
format Preprint
id arxiv_https___arxiv_org_abs_2511_05316
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A subpopulation of low-mass, spinning black holes: signatures of dynamical assembly
Tong, Hui
Callister, Thomas A.
Fishbach, Maya
Thrane, Eric
Antonini, Fabio
Stevenson, Simon
Romero-Shaw, Isobel M.
Dosopoulou, Fani
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Gravitational-wave observations of massive, rapidly spinning binary black holes mergers provide increasing evidence for the dynamical origin of some mergers. Previous studies have interpreted the mergers with primary mass $\gtrsim45\,M_\odot$ as being dominated by hierarchical, second-generation mergers, with rapidly spinning primaries being the products of previous black hole mergers assembled in dense stellar clusters. In this work, we reveal confident evidence of another subpopulation with rapid and isotropic spins at low mass containing the two exceptional events GW241011 and GW241110, consistent with a hierarchical merger hypothesis. Our result suggests the mass distribution of the second-generation black holes is peaked at low primary masses of $\sim16\,M_\odot$ rather than $\gtrsim45\,M_\odot$ in the pair-instability gap. Such low-mass second-generation black holes must be formed from the merger of even lighter first-generation black holes, implying that dense, metal-rich stellar environments contribute to the binary black hole population. By separating the contamination of higher-generation black holes, our result reveals the primary mass distribution of first-generation black holes formed from stellar collapse, which shows a significant dip between $\sim12\,M_\odot$ to $\sim20\,M_\odot$. This may indicate a dearth of black holes due to variation in the core compactness of the progenitor.
title A subpopulation of low-mass, spinning black holes: signatures of dynamical assembly
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2511.05316