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

Abstract

In \citep{Qin+}, we attempted to reconstruct the weak lensing convergence map $\hatκ$ from cosmic magnification by linearly weighting the DECaLS galaxy overdensities in different magnitude bins of $grz$ photometry bands. The $\hatκ$ map is correlated with cosmic shear at 20-$σ$ significance. However, the low galaxy number density in the DECaLS survey prohibits the measurement of $\hatκ$ 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 $0.4<z_κ<0.6,0.6<z_κ<0.8$ and $0.8<z_κ<1.0$ respectively. More remarkably, the $\hatκ-\hatκ$ correlations of the $0.4<z_κ<0.6$ and $0.6<z_κ<0.8$ bins show reasonably good agreement with predictions based on theoretical interpretation of $\hatκ-γ$ measurement. This result takes a step further towards the cosmological application of our lensing reconstruction method.

14 pages, 10 figures