The cosmology dependence of the cluster weak-lensing mass bias

Context. Measurements of the shear induced by weak gravitational lensing around galaxy cluster lines of sight are the gold standard for calibrating cluster observable–mass relations, enabling a robust and precise inference of cosmological parameters. The “weak-lensing mass bias” is the systematic offset between the true halo mass and the mass that is inferred from the lensing data using an imperfect model for the halo mass distribution. Aims. We studied the impact of cosmology on the lensing mass bias to inform future cosmological analyses of galaxy clusters. Methods. We created synthetic lensing shear maps for 115 920 projections of clusters with M 200c > 1.56 × 10 14 h −1 M ⊙ in a suite of M AGNETICUM simulations. The simulation boxes are 896 h −1 Mpc per side and are set up with 15 different combinations of the cosmological parameters Ω m , Ω b , σ 8 , and H 0 . Assuming a Navarro–Frenk–White profile, we extracted “weak-lensing mass” measurements and quantified their bias ( b WL ) with respect to the true halo mass. To investigate the impact of baryonic effects, we performed the analysis on gravity-only simulations and on their full-physics hydrodynamical counterparts. Results. We confirm that assuming a fixed halo concentration or a fixed concentration–mass relation leads to cosmology-dependent changes in the mass bias. We report changes of up to Δln b WL = 0.030 with respect to the bias obtained at the fiducial WMAP7 cosmology. Adopting a model for the concentration that also depends on cosmology absorbs the changes in halo profiles, and we recover essentially constant values for the mass bias. Our analysis of hydrodynamical simulations suggests that future, more accurate models will also need to explicitly account for the strength of baryonic effects. Conclusions. The variation in the cluster weak-lensing mass bias over the range of cosmological parameters we probe here is small compared to the overall systematic error budget in current cluster lensing analyses. Nonetheless, we recommend the use of a model for halo concentration that explicitly depends on cosmology.