Scatter and bias in weak lensing selected clusters

TL;DR

This paper investigates the scatter and bias in weak lensing selected galaxy clusters, analyzing how dark matter distribution diversity affects peak detection and cluster orientation bias, with improved analytic models matching simulations and observations.

Contribution

It introduces an analytic model accounting for dark matter halo diversity and orientation bias, improving predictions of weak lensing peak counts and their relation to cluster mass.

Findings

Peak heights poorly correlate with virial mass but better with spherical overdensity mass.

Halo shape noise is comparable to shape and cosmic shear noise.

Weak lensing selected clusters tend to align their major axes with the line of sight.

Abstract

We examine scatter and bias in weak lensing selected clusters, employing both an analytic model of dark matter haloes and numerical mock data of weak lensing cluster surveys. We pay special attention to effects of the diversity of dark matter distributions within clusters. We find that peak heights of the lensing convergence map correlates rather poorly with the virial mass of haloes. The correlation is tighter for the spherical overdensity mass with a higher mean interior density. We examine the dependence of the halo shape on the peak heights, and find that the rms scatter caused by the halo diversity scales linearly with the peak heights with the proportionality factor of 0.1-0.2. The noise originated from the halo shape is found to be comparable to the source galaxy shape noise and the cosmic shear noise. We find the significant halo orientation bias, i.e., weak lensing selected clusters on average have their major axes aligned with the line-of-sight direction. We compute the orientation bias using an analytic triaxial halo model and obtain results quite consistent with the ray-tracing results. We develop a prescription to analytically compute the number count of weak lensing peaks taking into account all the main sources of scatters in peak heights. We find that the improved analytic predictions agree well with the simulation results for high S/N peaks. We also compare the expected number count with our weak lensing analysis results for 4 sq deg of Subaru/Suprime-Cam observations and find a good agreement.