μ* masses: Weak-lensing calibration of the dark energy survey year 1 redMaPPer clusters using stellar masses

We present the weak-lensing mass calibration of the stellar-mass-based μ mass proxy for redMaPPer galaxy clusters in the Dark Energy Survey Year 1. For the first time, we are able to perform a calibration of μ at high redshifts, z > 0.33. In a blinded analysis, we use ∼6000 clusters split into 12 subsets spanning the ranges 0.1 ≤ z < 0.65 and μ up to ∼5.5 × 1013 M, and infer the average masses of these subsets through modelling of their stacked weak-lensing signal. In our model, we account for the following sources of systematic uncertainty: shear measurement and photometric redshift errors, miscentring, cluster-member contamination of the source sample, deviations from the Navarro-Frenk-White halo profile, halo triaxiality, and projection effects. We use the inferred masses to estimate the joint mass-μz scaling relation given by M200c|μ, z = M0(μ5.16 × 1012 M)Fμ ((1 + z)/1.35)Gz. We find M0 = (1.14 ± 0.07) × 1014 M with Fμ= 0.76 ± 0.06 and Gz = −1.14 ± 0.37. We discuss the use of μ as a complementary mass proxy to the well-studied richness λ for: (i) exploring the regimes of low z, λ < 20 and high λ, z ∼ 1; and (ii) testing systematics such as projection effects for applications in cluster cosmology