The Effect of Systematic Redshift Biases in BAO Cosmology

Abstract

With the remarkable increase in scale and precision provided by upcoming galaxy redshift surveys, systematic errors that were previously negligible may become significant. In this paper, we explore the potential impact of low-magnitude systematic redshift offsets on measurements of the Baryon Acoustic Oscillation (BAO) feature, and the cosmological constraints recovered from such measurements. Using 500 mock galaxy redshift surveys as our baseline sample, we inject a series of systematic redshift biases (ranging from ±0.2% to ±2%), and measure the resulting shift in the recovered isotropic BAO scale. When BAO measurements are combined with CMB constraints (in both ΛCDM and 𝑤CDM cosmologies), plausible systematics introduce a negligible offset on combined fits of 𝐻 0 and Ω 𝑚 , and systematics must be an order of magnitude greater than this plausible baseline to introduce a 1𝜎 shift on such combined fits. We conclude that systematic redshift biases are very unlikely to bias constraints on parameters such as 𝐻 0 provided by BAO cosmology, either now or in the near future. We also detail a theoretical model that predicts the impact of uniform redshift systematics on 𝛼, and show this model is in close alignment with the results of our mock survey analysis.

Improving NASA/IPAC Extragalactic Database Redshift Calculations

“…While the error is small and will have been negligible for most applications (e.g. Glanville et al 2020), it is important to fix since systematic effects could propagate out to inferred cosmological parameters (Wojtak et al 2015;Calcino & Davis 2017;Chaves-Montero et al 2018;Steinhardt et al 2020).…”