Prospects for measuring dark energy with 21 cm intensity mapping experiments

Abstract

Using the 21 cm intensity mapping (IM) technique can efficiently perform large-scale neutral hydrogen (H i) survey, and thus can detect the baryon acoustic oscillation (BAO) signals in the large-scale H i distribution. This method has great potential for measuring dark-energy parameters. Some 21 cm IM experiments have been proposed and performed, of which the typical ones include BINGO, FAST, SKA1, HIRAX, CHIME, and Tianlai. In this work, we make a forecast for these typical 21 cm IM experiments in their capability of measuring parameters of dark energy. We find that the interferometers have great advantages in constraining cosmological parameters. In particular, the Tianlai cylinder array alone can achieve the standard of precision cosmology for the ΛCDM model. However, for constraining dynamical dark energy, we find that SKA1-MID performs very well (using its single-dish mode). In addition, we show that the simulated 21 cm IM data can break the parameter degeneracies inherent in the CMB data, and CMB+SKA1 offers σ(w) = 0.013 in the wCDM model, and σ(w0) = 0.080 and σ(wa) = 0.25 in the CPL model. Compared with CMB+BAO+SN, Tianlai can provide tighter constraints in ΛCDM and wCDM, but looser constraints (tighter than CMB+BAO) in CPL, and the combination CMB+BAO+SN+Tianlai gives σ(w) = 0.013, σ(w0) = 0.055, and σ(wa) = 0.13. Finally, we find that the residual foreground contamination amplitude has a considerable impact on constraint results. We show that in the future 21 cm IM experiments will provide a powerful probe for exploring the nature of dark energy.