Model-Independent Test for Gravity using Intensity Mapping and Galaxy Clustering

TL;DR

This paper introduces a new clustering-based method to measure the $E_G$ statistic, enabling robust tests of General Relativity using intensity mapping and galaxy clustering without relying on lensing data.

Contribution

It presents a novel estimator for $E_G$ that uses only clustering information from intensity mapping and galaxy surveys, reducing contamination issues.

Findings

Forecasts a 7% precision measurement of $E_G$ with upcoming surveys.

Demonstrates suppression of contaminations affecting other estimators.

Provides a robust test of General Relativity using clustering data.

Abstract

We propose a novel method to measure the $E_G$ statistic from clustering alone. The $E_G$ 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 $E_G$ 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 $E_G$, 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 $E_G$ 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 $E_G$ with a precision of up to 7% (3.9% for the more futuristic SKA2).