The shear measurement from DECaLS (Dark Energy Camera Legacy Survey) provides an excellent opportunity for galaxy-galaxy lensing study with DESI (Dark Energy Spectroscopic Instrument) galaxies, given the large (∼9000 deg2) sky overlap. We explore this potential by combining the DESI 1\% survey and DECaLS DR8. With ∼106 deg2 sky overlap, we achieve significant detection of galaxy-galaxy lensing for BGS and LRG as lenses. Scaled to the full BGS sample, we expect the statistical errors to improve from 18(12)% to a promising level of 2(1.3)% at θ>8′(<8′). This brings stronger requirements for future systematics control. To fully realize such potential, we need to control the residual multiplicative shear bias ∣m∣<0.01 and the bias in the mean redshift ∣Δz∣<0.015. We also expect significant detection of galaxy-galaxy lensing with DESI LRG/ELG full samples as lenses, and cosmic magnification of ELG through cross-correlation with low-redshift DECaLS shear. {If such systematical error control can be achieved,} we find the advantages of DECaLS, comparing with KiDS (Kilo Degree Survey) and HSC (Hyper-Suprime Cam), are at low redshift, large-scale, and in measuring the shear-ratio (to σR∼0.04) and cosmic magnification.
@article{arxiv.2301.13434,
title = {DESI and DECaLS (D&D): galaxy-galaxy lensing measurements with 1% survey and its forecast},
author = {Ji Yao and Huanyuan Shan and Pengjie Zhang and Eric Jullo and Jean-Paul Kneib and Yu Yu and Ying Zu and David Brooks and Axel de la Macorra and Peter Doel and Andreu Font-Ribera and Satya Gontcho A Gontcho and Theodore Kisner and Martin Landriau and Aaron Meisner and Ramon Miquel and Jundan Nie and Claire Poppett and Francisco Prada and Michael Schubnell and Mariana Vargas Magana and Zhimin Zhou},
journal= {arXiv preprint arXiv:2301.13434},
year = {2023}
}