Gravitational wave standard sirens from GWTC-3 combined with DESI DR2 and DESY5: A late-universe probe of the Hubble constant and dark energy

Recently, the combination of the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) baryon acoustic oscillation (BAO) data and the Planck cosmic microwave background (CMB) measurements has shown a $\sim3\sigma$ preference for a dynamical dark energy model with a phantom-crossing behavior. However, such a phantom-crossing dark energy evolution from $w-1$ further exacerbates the already severe Hubble tension in the $\Lambda$CDM model. Moreover, there exists a $\sim2\sigma$ tension between the DESI DR2 BAO and CMB datasets. Therefore, it is essential to measure the Hubble constant and dark-energy equation-of-state (EoS) parameters using only late-universe observations. In this work, we investigate a novel late-universe data combination: gravitational-wave (GW) standard sirens, BAO, and Type Ia supernovae (SNe Ia). This combination provides a fully distance-ladder- and CMB-independent determination of the Hubble constant and the dark-energy EoS. Using 47 GW standard sirens from the third Gravitational-Wave Transient Catalog, the DESI DR2 BAO data, and DESY5 SNe Ia data, in the $w_0w_a$CDM model, we obtain $H_0=74.8^{+6.3}_{-8.9}{\rm~km~s^{-1}Mpc^{-1}}$, $\Omega_{\rm~m}=0.320^{+0.015}_{-0.012}$, $w_0=-0.775^{+0.072}_{-0.074}$, and $w_a=-0.80\pm0.47$, indicating a mild phantom-crossing behavior within the $1\sigma$ credible interval with an $H_0$ value consistent with the distance ladder measurements. Our analysis demonstrates the power of GW standard sirens in breaking parameter degeneracies, and for the first time, achieves robust joint constraints on the Hubble constant and the dark-energy EoS parameters based on real GW data.