Model-independent test for gravity using intensity mapping and galaxy clustering

We propose a novel method to measure the EG statistic from clustering alone. The EG statistic provides an elegant way of testing the consistency of General Relativity by comparing the geometry of the Universe, probed through gravitational lensing, with the motion of galaxies in that geometry. Current EG estimators combine galaxy clustering with gravitational lensing, measured either from cosmic shear or from CMB lensing. In this paper, we construct a novel estimator for EG, using only clustering information obtained from two tracers of the large-scale structure: intensity mapping and galaxy clustering. In this estimator, both the velocity of galaxies and gravitational lensing are measured through their impact on clustering. We show that with this estimator, we can suppress the contaminations that affect other EG estimators and consequently test the validity of General Relativity robustly. We forecast that with the coming generation of surveys like HIRAX and Euclid, we will measure EG with a precision of up to 7% (3.9% for the more futuristic SKA2).

Automated summary

We propose a new method to measure the EG statistic solely based on clustering. This method can test the consistency of General Relativity by comparing the geometry of the Universe through gravitational lensing with the motion of galaxies. Instead of combining galaxy clustering with gravitational lensing, our method uses clustering information from intensity mapping and galaxy clustering to construct an estimator for EG. With this estimator, we can effectively suppress contaminations and robustly test the validity of General Relativity. We forecast that upcoming surveys like HIRAX and Euclid can achieve a precision of up to 7% (3.9% for SKA2) in measuring EG.