Orateur
Description
Gravitational lensing magnification affects the observed spatial distribution of galaxies and must be accounted for to avoid biases in cosmological probes of large-scale structure. I will present the methodology used to evaluate its impact on the Dark Energy Survey Year 6 (DES Y6) galaxy clustering and galaxy-galaxy lensing analyses. We quantify the redshift-dependent magnification bias using the Balrog synthetic source injection catalog, accounting for the complexity of the galaxy sample selection function. We investigate the impact of magnification on cosmological constraints by testing different priors on magnification bias parameters. Our results show that magnification is a significant systematic for the Y6 fiducial lens sample (MagLim++) and must be addressed. Additionally, we demonstrate that including clustering cross-correlations between lens bins in the analysis enhances constraints on magnification parameters, enabling the use of uninformative priors. While magnification has minimal effect on the precision of cosmological constraints, neglecting it introduces parameter biases that can exceed statistical uncertainties, making its correction critical for current and future weak lensing surveys.
