Weak Lensing Reconstruction by Counting Galaxies: Improvement with DES Y3 Galaxies

TL;DR

This paper improves weak lensing convergence map reconstruction using galaxy counts by applying the method to DES Y3 data, achieving significant detection of cross-correlations and consistency with theoretical predictions, advancing cosmological applications.

Contribution

The paper demonstrates the application of galaxy-count-based weak lensing reconstruction to DES Y3 data, showing improved detection and consistency with theory, advancing the method's cosmological utility.

Findings

Detection of convergence-shear cross-correlation signals with high significance.

Reasonable agreement of $ ext{auto-} ext{kappa}$ correlations with theoretical predictions.

Enhanced galaxy number density enables better lensing map reconstruction.

Abstract

In \citep{Qin+}, we attempted to reconstruct the weak lensing convergence map $\hat{\kappa}$ from cosmic magnification by linearly weighting the DECaLS galaxy overdensities in different magnitude bins of $grz$ photometry bands. The $\hat{\kappa}$ map is correlated with cosmic shear at 20-$\sigma$ significance. However, the low galaxy number density in the DECaLS survey prohibits the measurement of $\hat{\kappa}$ auto-correlation. In this paper, we apply the reconstruction method to the Dark Energy Survey Year 3 (DES Y3) galaxies from the DES Data Release 2 (DR2). With greater survey depth and higher galaxy number density, convergence-shear cross-correlation signals are detected with $S/N\approx 9,16,20$ at $0.4<z_\kappa<0.6,0.6<z_\kappa<0.8$ and $0.8<z_\kappa<1.0$ respectively. More remarkably, the $\hat{\kappa}-\hat{\kappa}$ correlations of the $0.4<z_\kappa<0.6$ and $0.6<z_\kappa<0.8$ bins show reasonably good agreement with predictions based on theoretical interpretation of $\hat{\kappa}-\gamma$ measurement. This result takes a step further towards the cosmological application of our lensing reconstruction method.