Cosmological distance forecasts for the CSST Galaxy Survey using BAO peaks

Abstract

The measurement of cosmological distances using baryon acoustic oscillations (BAO) is crucial for studying the universe’s expansion. The China Space Station Telescope (CSST) galaxy redshift survey, with its vast volume and sky coverage, provides an opportunity to address key challenges in cosmology. However, redshift uncertainties in galaxy surveys can degrade both angular and radial distance estimates. In this study, we forecast the precision of BAO distance measurements using mock CSST galaxy samples, applying a two-point correlation function (2PCF) wedge approach to mitigate redshift errors. We simulate redshift uncertainties of σ₀ = 0.003 and σ₀ = 0.006, representative of expected CSST errors, and examine their effects on the BAO peak and distance scaling factors, α_⊥ and α_∥, across redshift bins within 0.0 < z ⩽ 1.0. The wedge 2PCF method proves more effective in detecting the BAO peak compared with the monopole 2PCF, particularly for σ₀ = 0.006. Constraints on the BAO peaks show that α_⊥ is well constrained around 1.0, regardless of σ₀, with precision between 1% and 3% across redshift bins. In contrast, α_∥ measurements are more sensitive to increases in σ₀. For σ₀ = 0.003, the results remain close to the fiducial value, with uncertainties ranging between 4% and 9%; for σ₀ = 0.006, significant deviations from the fiducial value are observed. We also study the ability to measure parameters (Ω_m, H₀r_d) using distance measurements, proving robust constraints as a cosmological probe under CSST-like redshift uncertainties. These findings demonstrate that the CSST survey enables few-percent precision measurements of D_A using the wedge 2PCF method, highlighting its potential to place tight constraints on the universe’s expansion history and contribute to high-precision cosmological studies.