Cluster magnification and the mass–richness relation in CFHTLenS

Abstract

Gravitational lensing magnification is measured with a significance of 9.7σ on a large sample of galaxy clusters in the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS). This survey covers ∼154 deg2 and contains over 18 000 cluster candidates at redshifts 0.2 ≤ z ≤ 0.9, detected using the 3D-Matched Filter cluster-finder of Milkeraitis et al. We fit composite-NFW models to the ensemble, accounting for cluster miscentring, source-lens redshift overlap, as well as nearby structure (the two-halo term), and recover mass estimates of the cluster dark matter haloes in range of ∼1013 M⊙ to 2 × 1014 M⊙. Cluster richness is measured for the entire sample, and we bin the clusters according to both richness and redshift. A mass–richness relation M200 = M0(N200/20)β is fit to the measurements. For two different cluster miscentring models, we find consistent results for the normalization and slope, M0 = (2.3 ± 0.2) × 1013 M⊙, β = 1.4 ± 0.1 and M0 = (2.2 ± 0.2) × 1013 M⊙, β = 1.5 ± 0.1. We find that accounting for the full redshift distribution of lenses and sources is important, since any overlap can have an impact on mass estimates inferred from flux magnification.