mu(*) 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 mu(*) mass proxy for redMaPPer galaxy clusters in the Dark Energy SurveyYear 1. For the first time, we are able to perform a calibration of mu(*) at high redshifts, z> 0.33. In a blinded analysis, we use similar to 6000 clusters split into 12 subsets spanning the ranges 0.1 <= z< 0.65 and mu(*) up to similar to 5.5 x 10(13) M-circle dot, 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-mu(*)-z scaling relation given by < M-200c vertical bar mu(*), z > = M0(mu(*)/5.16 x 10(12)M(circle dot))F-mu* ((1 + z)/1.35)(Gz). We find M-0 = (1.14 +/- 0.07) x 10(14)M(circle dot) with F mu(*) = 0.76 +/- 0.06 and G(z) = -1.14 +/- 0.37. We discuss the use of mu(*) as a complementary mass proxy to the well-studied richness. for: (i) exploring the regimes of low z, lambda < 20 and high lambda, z similar to 1; and (ii) testing systematics such as projection effects for applications in cluster cosmology.