Late-time cosmology with 21cm intensity mapping experiments

TL;DR

This paper forecasts the potential of 21cm intensity mapping experiments to constrain key cosmological parameters at low to intermediate redshifts, comparing their effectiveness with optical surveys and analyzing systematic challenges.

Contribution

It introduces a framework for forecasting cosmological constraints from 21cm intensity mapping and compares these with optical galaxy surveys, including systematic effects analysis.

Findings

SKA Phase I could match Euclid's dark energy constraints

Controlling autocorrelation calibration is crucial for success

21cm surveys can provide competitive cosmological measurements

Abstract

We present a framework for forecasting cosmological constraints from future neutral hydrogen intensity mapping experiments at low to intermediate redshifts. In the process, we establish a simple way of comparing such surveys with optical galaxy redshift surveys. We explore a wide range of experimental configurations and assess how well a number of cosmological observables (the expansion rate, growth rate, and angular diameter distance) and parameters (the densities of dark energy and dark matter, spatial curvature, the dark energy equation of state, etc.) will be measured by an extensive roster of upcoming experiments. A number of potential contaminants and systematic effects are also studied in detail. The overall picture is encouraging -- if autocorrelation calibration can be controlled to a sufficient level, Phase I of the SKA should be able to constrain the dark energy equation of state about as well as a DETF Stage IV galaxy redshift survey like Euclid, in roughly the same timeframe.