This paper reports what the LIGO–Virgo–KAGRA collaborations learn about the population of merging compact binaries from the latest catalog, called GWTC-5.0. The authors analyze 267 candidate mergers detected to date. Because the new data set contains no new confident neutron-star events, the paper focuses mostly on binary black holes — pairs of black holes that merge and produce gravitational waves.

The team used hierarchical Bayesian inference to combine information from all events while accounting for which events the detectors could have found. They considered events from the fourth observing run, including 104 new binary black hole detections from the second half of that run. The population study uses standard assumptions in the catalog: signals come from nearly circular orbits, and parameter estimates are reweighted to a common prior. To reduce false alarms, the analysis includes only events that exceed a false-alarm-rate threshold (less than 1 per year for black-hole-only studies).

Key quantitative results include an overall local merger rate for binary black holes with component masses between 2.5 and 200 solar masses of about 27.5–49.4 per cubic gigaparsec per year (this interval is the 90% credible range and is quoted at redshift z = 0.2). The mass distribution shows two notable features: a peak near 10 solar masses and a change in slope around 35 solar masses. Above about 40 solar masses the smaller object in the pair (the secondary) becomes rarer more quickly than the larger one (the primary), indicating that very massive primaries tend to pair with much lighter companions.

The spin measurements also show structure. Most black holes have modest spin magnitudes: about 69–84% are inferred to have dimensionless spin χ ≤ 0.5 (χ is a way to say how fast a black hole rotates, on a scale where 1 is the maximum in general relativity). The distribution of the effective inspiral spin parameter, χ_eff (a single number that captures how the two spins line up with the orbital motion), is centered near zero but is asymmetric. From this asymmetry the authors infer that at least about 9% of mergers come from formation channels that tend to align spins with the orbit. They also find evidence for a subpopulation containing at least one rapidly spinning black hole (χ ≈ 0.7). These rapid-spin mergers appear at two mass ranges: primary masses around 10–20 solar masses and above roughly 45 solar masses. The inferred merger rate of that rapid-spin subset is about 0.2–3.11 Gpc^−3 yr^−1 at z = 0.2.