Forecasting the E_G measurements from the photometric and spectroscopic surveys of Chinese Space Station Survey Telescope (CSST)

TL;DR

This paper forecasts the ability of the upcoming Chinese Space Station Survey Telescope (CSST) to measure the $E_G$ statistic, which tests gravity, showing it will significantly improve current constraints and help distinguish modified gravity models.

Contribution

The study provides the first detailed forecast of $E_G$ measurements from CSST, highlighting its potential to constrain modified gravity parameters with high precision.

Findings

CSST can achieve 3%-9% $E_G$ constraints over $0<z<1.2

Constraints on $oldsymbol{\Sigma_0}$ can reach about 5%

With 1% $eta$ accuracy, $E_G$ constraints improve to percent level

Abstract

We present forecasts for the $E_G$ statistic using redshift distributions of realistic mock galaxy samples from the upcoming Chinese Space Station Survey Telescope (CSST). The dominant uncertainty in $E_G$ stems from the redshift space distortion parameter ${\beta}$, whose precision limits the overall constraining power. Our analysis shows that CSST will nevertheless achieve $E_G$ constraints at the few-percent level (3%-9%) over $0 < z < 1.2$, an improvement by a factor of several to an order of magnitude over current observations. Within the $\mu-\Sigma$ modified gravity framework, the parameter $\Sigma_0$, associated with the effective gravitational constant of the Weyl potential, can be constrained to $\sim 5\%$ precision. In a plausible scenario where upcoming spectroscopic surveys determine ${\beta}$ to 1\% accuracy, $E_G$ constraints tighten to the percent level, and $\Sigma_0$ becomes measurable at $\sim 1\%$. These results demonstrate that CSST will serve as a powerful facility for testing gravity and underscore the essential synergy between photometric weak lensing and spectroscopic surveys in probing cosmic acceleration.