Taiji-TianQin-LISA network: Precisely measuring the Hubble constant using both bright and dark sirens

• Published in: Science China. Physics, mechanics & astronomy mechanics & astronomy, 2024-02, Vol.67 (2), p.220412, Article 220412
• Main Authors: Jin, Shang-Jie, Zhang, Ye-Zhu, Song, Ji-Yu, Zhang, Jing-Fei, Zhang, Xin
• Format: Article
• Language: English
• Subjects: Astronomy; Black holes; Classical and Continuum Physics; Dark energy; Gravitational waves; Hubble constant; Mathematical models; Observations and Techniques; Parameters; Physics; Physics and Astronomy; Sirens
• ISSN: 1674-7348; 1869-1927
• DOI: 10.1007/s11433-023-2276-1

In the coming decades, the space-based gravitational-wave (GW) detectors such as Taiji, TianQin, and LISA are expected to form a network capable of detecting millihertz GWs emitted by the mergers of massive black hole binaries (MBHBs). In this work, we investigate the potential of GW standard sirens from the Taiji-TianQin-LISA network in constraining cosmological parameters. For the optimistic scenario in which electromagnetic (EM) counterparts can be detected, we predict the number of detectable bright sirens based on three different MBHB population models, i.e., pop III, Q3d, and Q3nod. Our results show that the Taiji-TianQin-LISA network alone could achieve a constraint precision of 0.9% for the Hubble constant, meeting the standard of precision cosmology. Moreover, the Taiji-TianQin-LISA network could effectively break the cosmological parameter degeneracies generated by the CMB data, particularly in the dynamical dark energy models. When combined with the CMB data, the joint CMB+Taiji-TianQin-LISA data offer σ ( w ) = 0.036 in the w CDM model, which is close to the latest constraint result obtained from the CMB+SN data. We also consider a conservative scenario in which EM counterparts are not available. Due to the precise sky localizations of MBHBs by the Taiji-TianQin-LISA network, the constraint precision of the Hubble constant is expected to reach 1.2%. In conclusion, the GW standard sirens from the Taiji-TianQin-LISA network will play a critical role in helping solve the Hubble tension and shedding light on the nature of dark energy.