On the cosmology dependence of the cluster weak-lensing mass bias

Abstract

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, thereby 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. We study the impact of cosmology on the lensing mass bias to inform future cosmological analyses of galaxy clusters. We create synthetic lensing shear maps for 115,920 projections of clusters with $M_{200\mathrm c}>1.56\times10^{14}\,h^{-1}M_\odot$ in a suite of Magneticum simulations. The simulation boxes are $896\,h^{-1}$Mpc on a side and are set up with 15 different combinations of the cosmological parameters $Ω_\mathrm{m}$, $Ω_\mathrm{b}$, $σ_8$, and $H_0$. Assuming a Navarro-Frenk-White profile, we extract weak-lensing mass measurements and quantify their bias $b_\mathrm{WL}$ with respect to the true halo mass. To investigate the impact of baryonic effects, we perform the analysis on gravity-only simulations and on their full-physics hydrodynamical counterparts. We confirm that assuming a fixed halo concentration or a fixed concentration-mass relation leads to cosmology-dependent changes of the mass bias. We report changes of up to $Δ\ln b_\mathrm{WL}=0.030$ 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.

Figures (11)

• Figure 1: Combinations of cosmological parameters for the 15 Box1a runs of the Magneticum simulation suite.
• Figure 2: Projected mass map along the $x$-axis for a dark-matter halo in the C9 simulation at redshift $z=0.3$. In our analysis, we also use the projections along the $y$ and $z$-axes.
• Figure 3: Maps of the convergence, the two Cartesian shear components, and the tangential and cross shear around the halo center. These maps show the same example halo as in Fig. \ref{['fig:massmap']}.
• Figure 4: Radial lensing profiles for the same example halo as in Figs. \ref{['fig:massmap']} and \ref{['fig:2d_lensing_maps']}. The three colors correspond to the profiles projected along the three Cartesian axes.
• Figure 5: Relationship between the halo mass and the lensing mass computed from the reduced shear profile for each halo. The top-hat filtered relation qualitatively follows the one-to-one relation, implying that the simplified model for the cluster shear is appropriate.