New Method for Measuring Cosmological Parameters Using Gravitational Waves

Researchers have demonstrated a new method for measuring cosmological parameters using gravitational waves (GWs) without relying on astrophysical models. The study, titled "No need to know: astrophysics-free gravitational-wave cosmology," was authored by Amanda M. Farah, Thomas A. Callister, Jose María Ezquiaga, Michael Zevin, and Daniel E. Holz .

The team applied a non-parametric model to a simulated catalog of 1,000 GW events, consistent with expectations for the next LIGO-Virgo-KAGRA (LVK) observing run. This approach allows for the accurate inference of cosmological parameters without prior assumptions about the shape of the mass distribution of compact binaries. The researchers predict a 5.8% measurement of the Hubble constant (H0) and a 6.4% measurement of the Hubble parameter at redshift 0.9 (H(z=0.9)), with 1σ uncertainties .

This method, termed the "spectral siren" technique, leverages features in the mass distribution of GW sources to provide self-calibrating redshift measurements. This eliminates the need for electromagnetic measurements or host galaxy associations, which are typically required in standard-siren cosmology .

The findings suggest that this astrophysically-agnostic technique will be crucial for obtaining precise and unbiased cosmological constraints from GW source populations. This advancement could significantly enhance our understanding of the Universe's expansion and the underlying cosmological parameters .