μ⋆ masses: weak-lensing calibration of the Dark Energy Survey Year 1 redMaPPer clusters using stellar masses

Abstract

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 ∼6, 000 clusters split into 12 subsets spanning the ranges 0.1 ≤ z < 0.65 and μ⋆ up to ∼5.5 × 1013M⊙, 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 NFW halo profile, halo triaxiality and projection effects. We use the inferred masses to estimate the joint mass–μ⋆–z scaling relation given by $\langle M_{200c} | \mu _{\star },z \rangle = M_0 (\mu _{\star }/5.16\times 10^{12} \mathrm{M_{\odot }})^{F_{\mu _{\star }}} ((1+z)/1.35)^{G_z}$. We find M0 = (1.14 ± 0.07) × 1014M⊙ with $F_{\mu _{\star }}= 0.76 \pm 0.06$ 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; ii) testing systematics such as projection effects for applications in cluster cosmology.

On the weak lensing masses of a new sample of galaxy groups

“…Stacking techniques effectively increase the signal-to-noise ratio of the shear measurements, allowing us to derive reliable average mass density distributions of the combined lenses (e.g. Leauthaud et al 2017;Simet et al 2017;Chalela et al 2018;Pereira et al 2020).…”

“…These relations are usually calibrated considering the masses estimated through the application of weak-lensing stacking techniques (e.g. Leauthaud et al 2010;Viola et al 2015;Simet et al 2017;Pereira et al 2018Pereira et al , 2020, since gravitational lensing provides a direct way to derive the average mass distribution for a sample of galaxy groups. These stacking techniques are based on the combination of groups within a range of a given observational property such as richness or total luminosity, in order to increase the signal-to-noise ratio of the lensing signal.…”

The effect of selection -- a tale of cluster mass measurement bias induced by correlation and projection

“…Galaxy clusters have long been utilized as sensitive probes of cosmology in optical wide-field surveys such as the Sloan Digital Sky Survey (Rozo et al 2010;Zu et al 2014;Costanzi et al 2019b), the Dark Energy Survey (Abbott et al 2020) and also planned for the upcoming Legacy Survey of Space and time at the Rubin Observatory (The LSST Dark Energy Science Collaboration et al 2018). These optical survey programs study galaxy clusters by their optical observables (e.g., Rykoff et al 2014;Palmese et al 2020) and weak lensing mass signals (Simet et al 2017;McClintock et al 2019;Pereira et al 2020), often to a lower mass threshold than X-ray and CMB experiments (e.g., Vikhlinin et al 2009;Mantz et al 2015;Planck Collaboration et al 2016;Bocquet et al 2019). However recent discoveries from the Dark Energy Survey in Abbott et al (2020) point to additional systematic effects that plague the accuracy of cluster cosmological constraints, which stem from previously undetected selection effects biasing cluster weak lensing mass measurements.…”

The WaZP galaxy cluster sample of the dark energy survey year 1

“…DES has produced galaxy cluster samples with the redMaPPer algorithm which were published in Rykoff et al (2016) and Mc-Clintock, T. & Varga, T. N. et al (2019), based on DES Science Verification and DES-Y1 data releases, respectively. These samples led to several studies focusing on the mass-richness relation (Melchior et al 2015;Saro et al 2015;Zhang et al 2016;Palmese et al 2016;Saro et al 2017;Melchior, P. & Gruen, D. et al 2017;Pereira et al 2018;McClintock, T. & Varga, T. N. et al 2019;Bleem et al 2020;Pereira et al 2020). Complementary analyses were also performed on cluster luminosity function (Zhang et al 2019b), baryon content (Chiu et al 2018), and cluster miscentering relative to X-ray detections (Zhang et al 2019a).…”