Cosmological Forecasts from the Baryon Acoustic Oscillations in 21cm Intensity Mapping

We use the baryon acoustic oscillation (BAO) feature in the angular power spectrum (APS) of the 21cm line of neutral hydrogen (HI) to constrain cosmological parameters. As the BAO shift parameter can only constrain the product of the Hubble constant and the sound horizon H₀rₛ, we combine our Fisher matrices with cosmic microwave background (CMB) Fisher matrices from the covariance of $Planck$ telescope to break this degeneracy. In particular, we find that the best constraints we can get with this method are on the Hubble parameter h, and the dark energy parameters w₀ and wₐ. Assuming a noise level as for the BINGO telescope, we find σₕ = 0.0055\;(0.8%) in the ΛCDM model. For the wCDM model, we find σₕ = 0.020\;(2.9%) and σw₀ = 0.075\;(7.5%). In the CPL parameterization, we find σₕ = 0.029\;(4.4%), σw₀ = 0.40\;(40%), and σwₐ = 1.7. Although these constraints improve those from $Planck$ alone, we observe the BINGO data will be more significant for the wCDM model. We also observe the constraints from the BAO only is not as strong as using the whole 21cm angular power spectrum, but it is less susceptible to systematic effects.