Explorations in Astronomy & Astrophysics

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

Abstract

Yu Song and Yi Zheng

We present forecasts for the EG statistic using redshift distributions of realistic mock galaxy samples from the upcoming Chinese Space Station Survey Telescope (CSST). The dominant uncertainty in EG stems from the redshift space distortion parameter β, whose precision limits the overall constraining power. Our analysis shows that CSST will nevertheless achieve EG 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 µ − Σ modified gravity framework, the parameter Σ0, associated with the effective gravitational constant of the Weyl potential, can be constrained to ∼ 5% precision. In a plausible scenario where, upcoming spectroscopic surveys determine β to 1% accuracy, EG constraints tighten to the percent level, and Σ0 becomes measurable at ∼ 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.

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