Evidence for Three Subpopulations of Merging Binary Black Holes at Different Primary Masses
read the original abstract
With the release of the fourth LIGO--Virgo--KAGRA gravitational-wave catalog (GWTC-4), we are starting to gain a detailed view of the population of merging binary black holes. The formation channels of these black holes is not clearly understood, but different formation mechanisms may lead to subpopulations with different properties visible in gravitational-wave data. Adopting a phenomenological approach, we find GWTC-4 data supports the presence of at least three subpopulations, each associated with a different range of black hole mass and with sharp transition boundaries between them. Each subpopulation is characterized by different distributions for either the mass ratios, the black-hole spin magnitudes or both. Subpopulation A with primary mass $m_1 \leq 27.7^{+4.1}_{-3.4} M_{\odot}$ ($90 \%$ credibility), is characterized by a nearly flat mass ratio distribution $q=m_2/m_1$, and by small spin magnitudes ($\chi \leq 0.5^{+0.1}_{-0.1}$). Subpopulation B with $27.7^{+4.1}_{-3.4} M_{\odot} \leq m_1 \leq 40.2^{+4.7}_{-3.2} M_{\odot}$, has a much sharper preference for mass ratio $q \approx 1$. Subpopulation C, with $m_1 \geq 40.2^{+4.7}_{-3.2} M_{\odot}$, has support for large spin magnitudes, and tentative support for mass ratios $q\approx0.5$. We interpret these transitions as evidence for multiple subpopulations, each potentially associated with a different formation pathways. We suggest potential formation scenarios for each subpopulations, and suggest that Subpopulation B may be associated with chemically homogeneous evolution or population III stars. Our findings for Subpopulation C are largely consistent with recent claims of hierarchical mergers, but with some curious differences in properties.
This paper has not been read by Pith yet.
Forward citations
Cited by 26 Pith papers
-
Population Properties of Binary Black Holes with Eccentricity
First joint population inference on binary black hole eccentricity from GWTC-4 bounds the eccentric branching ratio below 5% at 90% confidence, with results consistent with quasi-circular models but highly model-dependent.
-
Reversible-jump MCMC reveals binary black hole subpopulations with distinct redshift evolution
Reversible-jump MCMC analysis of LIGO binary black hole mergers identifies three subpopulations with distinct properties and independent redshift evolution.
-
Secondary-Mass Features improve Spectral-Siren $H_0$ Constraints
A new model emphasizing secondary mass features and pairing transitions improves spectral siren H0 constraints by ~30% using 142 GW events from GWTC-4.0.
-
Joint population and strong-lensing inference for resolved gravitational-wave events probes the black-hole merger rate beyond the peak of star formation
Joint strong-lensing and population inference on resolved gravitational-wave events finds no lensed events and tightens constraints on the black-hole merger rate peak redshift and high-redshift tail.
-
Getting Tilted: Random Walk of Binary Black Hole Spin-Orbit Alignment in Dense Star Clusters
Models BBH spin-orbit alignment as random walk on sphere, deriving exact distribution after n encounters and showing alignment survives several strong encounters before isotropy.
-
Evidence for mass-dependent spin subpopulations in GWTC-4
GWTC-4 data supports two mass-dependent spin subpopulations: low-mass binaries mostly slow-spinning, high-mass ones dominated by moderate-to-rapid spins with transition from 35 to 70 solar masses.
-
A Strongly Parametrized Mass Ratio Model for the Stable Mass Transfer Channel: a Case Study of the $10 \, \rm{M}_{\odot}$ Peak
A parametrized analytical model for BBH mass ratios from the stable mass transfer channel is derived and applied to the 10 solar-mass peak in GWTC-4, favoring little mass-ratio reversal.
-
Second-Generation Mass Peak in the Gravitational-Wave Population as a Probe of Globular Clusters
Dynamical formation in globular clusters produces a robust second black-hole mass peak at ~70 solar masses from second-generation mergers when the first-generation spectrum is truncated by pair-instability supernovae.
-
Measurement prospects for the pair-instability mass cutoff with gravitational waves
Simulations show a 40-50 solar-mass black-hole cutoff is not guaranteed to be confidently recovered from GWTC-4-like catalogs, spurious detections are unlikely, and O4 data would reduce cutoff-mass uncertainty by at l...
-
Signatures of a subpopulation of hierarchical mergers in the GWTC-4 gravitational-wave dataset
GWTC-4 data show a transition to nearly all hierarchical mergers above 46 solar masses, with the hierarchical rate peaking at 15.7 solar masses, indicating mass-dependent substructure in black hole spins.
-
A new group of low-spin $50-70M_\odot$ Black Holes and the high pair-instability mass cutoff
GWTC-4.0 data shows low-spin black holes up to 70 solar masses, moving the low-spin cutoff to 68.5 solar masses and favoring a high pair-instability mass gap.
-
A Stellar Role Reversal: Multiple Features in the Mass and Mass Ratio Distributions of Merging Binary Black Holes from Stable Mass Transfer
Stable mass transfer produces two distinct peaks in merging binary black hole primary mass and mass ratio distributions via mass ratio reversal under conservative mass transfer.
-
Population-level correlations in Bayesian statistics: an illustrative model for gravitational-wave astronomy
An idealized Gaussian model demonstrates that single-event correlations inflate uncertainties in population correlations and that catalog-wide correlated biases can be misread as population correlations.
-
The Chirp-Mass Ladder: A New Rung Emerges
The chirp-mass distribution of GW-detected binary black holes shows a ladder of peaks doubling in mass, with a new intermediate peak at 19 solar masses confirming a prior prediction from the hierarchical merger model.
-
Targeting black holes from metal-poor progenitors with next-generation gravitational-wave detectors
Introduces a target redshift z_t to isolate metal-poor black hole progenitors and a statistical framework to test merger-rate variations against forecasts from Einstein Telescope and Cosmic Explorer.
-
BBH-Genesis: Disentangling Binary Black Hole Formation Channels with GWTC-4
BBH-Genesis applied to GWTC-4 finds strongest support for a two-channel model of binary black hole populations with possible mild evidence for an AGN-related third channel.
-
Compactness Peaks and Subpopulations: Probing Stellar Physics and Formation Channels of Merging Binary Black Holes
A stripped-star-motivated five-component model for binary black hole populations is preferred over the LVK baseline by a log10 Bayes factor of 7.69 and attributes the observed mass features to isolated, dynamical, and...
-
How do the LIGO-Virgo-KAGRA's Heavy Black Holes Form? No evidence for core-collapse Intermediate-mass black holes in GWTC-4
No evidence for core-collapse formed low-spin IMBHs in GWTC-4, with 90% upper limit on merger rate of 0.077 Gpc^{-3} yr^{-1}, low-spin BH mass truncation at 65 solar masses consistent with pair-instability gap lower e...
-
How do the LIGO-Virgo-KAGRA's Heavy Black Holes Form? No evidence for core-collapse Intermediate-mass black holes in GWTC-4
No evidence for core-collapse IMBHs in GWTC-4; heavy BHs from hierarchical mergers, with low-spin mass distribution truncating at ~65 solar masses and PIMG upper edge estimated at 150 solar masses.
-
Emergent structure in the binary black hole mass distribution and implications for population-based cosmology
B-spline agnostic reconstruction of binary black hole masses from GWTC-4.0 reveals multiple features and a logarithmic hierarchy that impacts Hubble constant measurements, with a low-mass subpopulation isolation metho...
-
Biased parameter inference of eccentric, spin-precessing binary black holes
Eccentric BBH signals recovered with quasi-circular precessing models show biases in chirp mass and χ_p; Bayes factors favor eccentric aligned-spin models when both eccentricity and precession are present.
-
When the black holes align: a subpopulation of aligned massive binary black holes observed via gravitational waves
Non-parametric analysis of GWTC-5.0 data supports multiple subpopulations of binary black holes distinguished by effective spin, with one aligned subpopulation suggesting dynamical formation.
-
Evidence for additional structure in the effective spin distribution hints at multiple formation pathways in GWTC-5.0
GWTC-5.0 analysis finds evidence for structure beyond a non-skewed Gaussian bulk in χ_eff, with suggestive mass-dependent excess of positive over negative spins outside the bulk at 13:1 odds in one mass bin.
-
No model-independent evidence for a peak in binary black hole spin (mis)alignments
No model-independent evidence for a peak in binary black hole spin tilts is found in GWTC-4; mass-spin magnitude correlation is confirmed but mass-tilt correlation is not.
-
Remnant recoil and host environments of GWTC-4.0 binary black-hole mergers
Five O4 gravitational-wave events prefer dynamical cluster formation; typical recoil kicks eject remnants from globular clusters but allow possible retention in nuclear star clusters, disfavoring efficient hierarchica...
-
The first decade of gravitational-wave measurements of black hole spins
A review summarizing formation-channel predictions, waveform effects, and population-level constraints on stellar-mass black hole spins from the first decade of gravitational-wave observations.
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.