Prospects for improving cosmological parameter estimation with gravitational-wave standard sirens from Taiji

Abstract

Taiji, a space-based gravitational-wave detector, consists of three satellites forming an equilateral triangle with arm length of 3 × 10 6 km, orbiting around the Sun. Taiji is able to observe standard siren events of massive black hole binary (MBHB) merger, which is helpful to probe the expansion of the universe. In this paper, we preliminarily forecast the capability of Taiji for improving cosmological parameter estimation with the gravitational-wave standard siren data. We simulate five-year standard siren data based on three fiducial cosmological models and three MBHB growth and formation models. It is found that the standard siren data from Taiji can effectively break the cosmological parameter degeneracies generated by the cosmic microwave background (CMB) anisotropies data, especially for dynamical dark energy models. The constraints on cosmological parameters are significantly improved by the data combination CMB+Taiji, compared to the CMB data alone. Compared to the current optical cosmological observations, Taiji can still provide help in improving the cosmological parameter estimation to some extent. In addition, we consider an ideal scenario to investigate the potential of Taiji on constraining cosmological parameters. We conclude that the standard sirens of MBHB from Taiji will become a powerful cosmological probe in the future.

Cosmological model-independent measurement of cosmic curvature using distance sum rule with the help of gravitational waves

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