Tomographic Alcock-Paczynski Method with Redshift Errors

TL;DR

The paper evaluates how redshift errors impact the tomographic Alcock-Paczynski method's effectiveness in constraining cosmology, finding it remains useful for future spectroscopic surveys despite some loss of precision.

Contribution

It provides a detailed analysis of redshift error effects on the tomographic AP method, demonstrating its robustness for future large-scale surveys.

Findings

Redshift errors mimic finger-of-god effects, smearing AP signals.

For $\sigma extless 0.002$, the loss in constraining power is under 50%.

Redshift errors can reduce RSD contamination, improving bias-to-signal ratio.

Abstract

The tomographic Alcock-Paczynski (AP) method is a promising method that uses the redshift evolution of the anisotropic clustering in redshift space to calibrate cosmology. It extends the applicable range of AP method to substantially nonlinear scales, yielding very tight cosmological constraints. For future stage-IV slitless spectroscopic surveys, the non-negligible redshift errors might reduce the advantage of the tomographic AP method by suppressing the resolution of the nonlinear structure along the line of sight. The present work studies how redshift errors propagate to cosmological parameters in the tomographic AP analysis. We use a formula $\sigma_z = \sigma(1+z)^{\alpha} $ to model the redshift errors, with $\sigma$ varying from 0.001 to 0.006 and $\alpha$ varying from 0.5 to 1.5. The redshift errors produce a signal of anisotropic clustering that is similar to a strong finger-of-god effect, which smears out both the AP signal and the contamination caused by the redshift space distortions (RSD). For the target precision of the Chinese Space Station Telescope optical survey ($\sigma\lesssim 0.002$), the decrement of constraining power on the dark energy equation of state is mild ($\lesssim 50\%$), and the suppression of RSD contamination leads to a smaller bias-to-signal ratio. Our results indicate that the tomographic AP method will remain a useful and complementary tool for analyses of future slitless spectroscopic surveys.