Future Cosmological Constraints from Fast Radio Bursts

TL;DR

This paper evaluates the potential of future Fast Radio Burst observations to improve cosmological parameter constraints, highlighting challenges from intergalactic medium inhomogeneities and the conditions under which FRBs can be most informative.

Contribution

It provides a forecast of FRBs' ability to constrain cosmological parameters using mock data and MCMC analysis, comparing their impact with existing and future surveys.

Findings

FRBs can improve constraints on baryon density when combined with other data.

IGM inhomogeneity causes significant scatter, limiting FRBs' utility.

FRBs offer valuable baryon density information independent of CMB data.

Abstract

We consider the possible observation of Fast Radio Bursts (FRBs) with planned future radio telescopes, and investigate how well the dispersions and redshifts of these signals might constrain cosmological parameters. We construct mock catalogues of FRB dispersion measure (DM) data and employ Markov Chain Monte Carlo (MCMC) analysis, with which we forecast and compare with existing constraints in the flat $\Lambda$CDM model, as well as some popular extensions that include dark energy equation of state and curvature parameters. We find that the scatter in DM observations caused by inhomogeneities in the intergalactic medium (IGM) poses a big challenge to the utility of FRBs as a cosmic probe. Only in the most optimistic case, with a high number of events and low IGM variance, do FRBs aid in improving current constraints. In particular, when FRBs are combined with CMB+BAO+SNe+$H_0$ data, we find the biggest improvement comes in the $\Omega_{\mathrm b}h^2$ constraint. Also, we find that the dark energy equation of state is poorly constrained, while the constraint on the curvature parameter $\Omega_k$, shows some improvement when combined with current constraints. When FRBs are combined with future BAO data from 21cm Intensity Mapping (IM), we find little improvement over the constraints from BAOs alone. However, the inclusion of FRBs introduces an additional parameter constraint, $\Omega_{\mathrm b}h^2$, which turns out to be comparable to existing constraints. This suggest that FRBs provide valuable information about the cosmological baryon density in the intermediate redshift Universe, independent of high redshift CMB data.