Prospects for measuring dark energy with 21 cm intensity mapping experiments: A joint survey strategy

The 21 cm intensity mapping (IM) technique provides us with an efficient way to observe the cosmic large-scale structure (LSS). From the LSS data, one can use the baryon acoustic oscillation and redshift space distortion to trace the expansion and growth history of the universe, and thus measure the dark energy parameters. In this paper, we make a forecast for cosmological parameter estimation with the synergy of three 21 cm IM experiments. Specifically, we adopt a novel joint survey strategy, FAST (0 < z < 0.35) + SKA1-MID (0.35 < z < 0.8) + HIRAX (0.8 < z < 2.5), to measure dark energy. We simulate the 21 cm IM observations under the assumption of excellent foreground removal. We find that the synergy of three experiments could place quite tight constraints on cosmological parameters. For example, it provides sigma(omega(m)) = 0.0039 and sigma(H-0) = 0.27 km s(-1) Mpc(-1) in the ACDM model. Notably, the synergy could break the cosmological parameter degeneracies when constraining the dynamical dark energy models. Concretely, the joint observation offers sigma(w) = 0.019 in the wCDM model, and sigma(w(0)) = 0.085 and sigma(w(a)) = 0.32 in the w(0)w(a)CDM model. These results are better than or equal to those given by CMB+BAO+SN. In addition, when the foreground removal efficiency is relatively low, the strategy still performs well. Therefore, the 21 cm IM joint survey strategy is promising and worth pursuing.

Automated summary

By using the synergy of three 21 cm intensity mapping experiments, the expansion and growth history of the universe can be traced, and the dark energy parameters can be measured within the framework of general relativity. This study finds that the joint observation of three experiments can provide tight constraints on cosmological parameters.