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

TL;DR

This paper forecasts cosmological parameter constraints using BAO signals from 21cm intensity maps, combining them with CMB data to improve precision, and assesses the benefits and challenges of using the full angular power spectrum.

Contribution

It introduces a template method for extracting BAO signals from 21cm maps and forecasts parameter constraints, combining with CMB data for improved accuracy.

Findings

Forecasted constraints on Hubble parameter and dark energy parameters.

Full APS yields tighter constraints than BAO-only analysis.

Combining 21cm BAO with CMB data breaks degeneracies.

Abstract

In this work we use a template method to extract the scale associated with the Baryon Acoustic Oscillation (BAO) signal in 21cm neutral hydrogen intensity maps. We then forecast the constraints on the standard deviations of cosmological parameters using a Fisher matrix analysis. In order to test this method, we choose the survey configuration for the BINGO telescope. We then estimate the constraints on the BAO shift parameter $\alpha$, which we extract from the 21cm angular power spectrum (APS). In addition, we translate those results into constraints on the final cosmological parameters. As BAO data alone can only constrain the product of the Hubble constant and the sound horizon $H_0r_s$, degeneracies between the variables mean that we can't get useful constraints with BAO data alone. We break these degeneracies by combining the 21cm intensity mapping BAO results with the Cosmic Microwave Background (CMB) covariances obtained by the Planck satellite. In particular, we find that the best forecasts we can get with this combination are on the standard deviations of the Hubble parameter $\sigma_h$, and the dark energy parameters $\sigma_{w_0}$ and $\sigma_{w_a}$. We find $\sigma_h = 0.0055\;(0.8\%)$ in the $\Lambda$CDM model. For the $w$CDM model, we find $\sigma_h = 0.020\;(2.9\%)$ and $\sigma_{w_0} = 0.075\;(7.5\%)$. In the CPL parameterization, we find $\sigma_h = 0.029\;(4.4\%)$, $\sigma_{w_0} = 0.40\;(40\%)$, and $\sigma_{w_a} = 1.7$. Finally, we observe that using the full APS provides stronger constraints than the BAO only, however, it is more susceptible to systematic effects.