Testing gravity at large scales with HI intensity mapping

TL;DR

This paper explores using HI intensity mapping to measure the $E_{G}$ statistic, enabling precise tests of Einstein's general relativity and alternative gravity models at large cosmological scales.

Contribution

It generalizes the $E_{G}$ estimator for HI intensity mapping and forecasts its potential to distinguish between GR and modified gravity models with upcoming surveys.

Findings

Fractional errors in $E_{G}$} measurements can be below 1%.

Upcoming surveys can effectively differentiate between GR and modified gravity.

HI intensity mapping with SKA offers precise tests of gravity at large scales.

Abstract

We investigate the possibility of testing Einstein's general theory of relativity (GR) and the standard cosmological model via the $E_{\rm G}$ statistic using neutral hydrogen (HI) intensity mapping. We generalise the Fourier space estimator for $E_{\rm G}$ to include HI as a biased tracer of matter and forecast statistical errors using HI clustering and lensing surveys that can be performed in the near future, in combination with ongoing and forthcoming optical galaxy and Cosmic Microwave Background (CMB) surveys. We find that fractional errors $< 1\%$ in the $E_{\rm G}$ measurement can be achieved in a number of cases and compare the ability of various survey combinations to differentiate between GR and specific modified gravity models. Measuring $E_{\rm G}$ with intensity mapping and the Square Kilometre Array can provide exquisite tests of gravity at cosmological scales.