2026/07/24 by Nir Guttman, Paul D. Lasky, Eric Thrane
Physics and Astronomy · #astro-ph.HE
17 pages, 5 figures
arxiv created 2026/07/30 · arxiv updated 2026/07/31
Gravitational-wave data are beginning to reveal a structured landscape of black-hole masses and spins, suggesting multiple formation processes are now being resolved observationally. We analyze data from LIGO--Virgo--KAGRA's (LVK's) fifth Gravitational-Wave Transient Catalog and find that the population is naturally described by four distinct subpopulations. The dominant component, contributing ≃70% of the astrophysical merger rate, is characterised by a low-mass population centred near 10M_\odot and is separated from heavier systems by a depletion near 14M_\odot. This component may be associated with black holes formed from failed supernovae. Above this depletion, we find two intermediate-mass components: an unequal-mass branch pairing the lower-mass, ≃10M_\odot black hole with a heavier black hole, perhaps associated with isolated-binary/stable-mass-transfer formation, and a nearly equal-mass branch peaking near 30--35M_\odot whose low spins and mass distribution favour first-generation systems possibly born in dense stellar environments. A fourth, percent-level component extends to higher masses and is characterized by a broad mass-ratio distribution and large spin magnitudes, consistent with a hierarchical-merger population. Our four-component model is overwhelmingly preferred over a standard LVK population model by a natural-log Bayes factor of ln(BF) = 19.2. Our work observationally unveils a new subpopulation of black-hole mergers utilising a new hybrid data-driven and parametric-model discovery method, bringing us one step closer to understanding stellar-mass black-hole archaeology.