Dark Energy Survey Year 3 results: cosmology from combined galaxy clustering and lensing -- validation on cosmological simulations

TL;DR

This paper validates the DES Year 3 cosmological analysis methods using sophisticated simulations, confirming their accuracy in recovering true cosmological parameters despite modeling uncertainties and photometric redshift errors.

Contribution

It introduces the Buzzard v2.0 simulations for validation and demonstrates the robustness of DES Y3 analysis choices and photometric redshift calibration methods.

Findings

Simulations accurately reproduce DES Y3 data aspects.

Model recovers true cosmology in simulated surveys.

Photometric redshift calibration is effective with realistic uncertainties.

Abstract

We present a validation of the Dark Energy Survey Year 3 (DES Y3) $3\times2$-point analysis choices by testing them on Buzzard v2.0, a new suite of cosmological simulations that is tailored for the testing and validation of combined galaxy clustering and weak lensing analyses. We show that the Buzzard v2.0 simulations accurately reproduce many important aspects of the DES Y3 data, including photometric redshift and magnitude distributions, and the relevant set of two-point clustering and weak lensing statistics. We then show that our model for the $3\times2$-point data vector is accurate enough to recover the true cosmology in simulated surveys assuming the true redshift distributions for our source and lens samples, demonstrating robustness to uncertainties in the modeling of the non-linear matter power spectrum, non-linear galaxy bias and higher-order lensing corrections. Additionally, we demonstrate for the first time that our photometric redshift calibration methodology, including information from photometry, spectroscopy, clustering cross-correlations, and galaxy-galaxy lensing ratios, is accurate enough to recover the true cosmology in simulated surveys in the presence of realistic photometric redshift uncertainties.