Joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations*

Abstract

Abstract Gravitational waves (GWs) from compact binary coalescences can be used as standard sirens to explore the cosmic expansion history. In the next decades, it is anticipated that we could obtain the multi-band GW standard siren data (from nanohertz to a few hundred hertz), which are expected to play an important role in cosmological parameter estimation. In this work, we provide, for the first time to the best of our knowledge, joint constraints on cosmological parameters using the future multi-band GW standard siren observations. We simulate the multi-band GW standard sirens based on the SKA-era pulsar timing array (PTA), Taiji observatory, and Cosmic Explorer (CE) to perform cosmological analysis. In the ΛCDM model, we find that the joint PTA+Taiji+CE data could provide a tight constraint on the Hubble constant with a precision. Moreover, PTA+Taiji+CE could break the cosmological parameter degeneracies generated by CMB, especially in the dynamical dark energy models. When combining the PTA+Taiji+CE data with the CMB data, the constraint precisions of and are and , respectively, meeting the standard of precision cosmology. The joint CMB+PTA+Taiji+CE data give in the wCDM model and and in the CDM model, which are comparable with or close to the latest constraint results by CMB+BAO+SN. In conclusion, the future multi-band GW observations are expected to be used for exploring the nature of dark energy and measuring the Hubble constant.