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Astrophysics

GWTC-5.0: Constraints on the Cosmic Expansion Rate and Modified Gravitational-wave Propagation

The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration

Featured May 28, 2026

Original Paper

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Simply

Combining gravitational-wave data with galaxy maps allows researchers to measure the universe's expansion rate more accurately than ever before, confirming that gravity behaves as expected on cosmic scales.

In depth
The paper utilizes the GWTC-5.0 catalog to perform a hierarchical Bayesian inference of the Hubble constant () by combining spectral siren information—derived from mass distribution features—with dark siren information from galaxy catalogs. This approach effectively breaks the mass-redshift degeneracy, allowing for a more precise cosmological measurement and rigorous testing of modified gravity theories that predict deviations from General Relativity in gravitational-wave propagation.

Key Takeaways

  • 1
    The study achieves an measurement of km s^{-1} Mpc^{-1}, representing a 25.7% reduction in uncertainty compared to previous catalogs.
  • 2
    Dark siren methods now provide tighter constraints than the single bright siren event GW170817, marking a significant milestone in gravitational-wave cosmology.
  • 3
    Parameterized tests of modified gravity propagation show no significant departures from General Relativity, consistent with standard cosmological predictions.

Conceptual Flow

HIGH LEVEL
1
Methodology

The researchers combine gravitational wave signals with galaxy maps to figure out how fast the universe is growing.

Gravitational Wave Data
Galaxy Catalog Maps
Hierarchical Bayesian Inference
Cosmological Parameters
2
Results

The study found that the universe is expanding at a specific rate and that gravity follows the rules of General Relativity.

GWTC-5.0 Catalog

Statistical Analysis

Hubble Constant