Weak lensing mass-richness relation of redMaPPer clusters in LSST DESC DC2 simulations

¹ Université Paris-Saclay, CEA, IRFU, 91191 Gif-sur-Yvette, France
² Université Grenoble Alpes, CNRS, IN2P3, LPSC, 38000 Grenoble, France
³ Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
⁴ Université Paris Cité, CNRS, IN2P3, APC, 75013 Paris, France
⁵ Italian National Institute of AstroPhysics, Osservatorio Astronomico di Trieste, Italy
⁶ Université de Savoie, CNRS, IN2P3, LAPP, Annecy-le-Vieux, France
⁷ Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA
⁸ Leinweber Center of Theoretical Physics, University of Michigan, Ann Arbor, MI 48109, USA
⁹ Department of Statistics and Data Sciences, The University of Texas at Austin, TX 78712, USA
¹⁰ The NSF-Simons AI Institute for Cosmic Origins, University of Texas at Austin, Austin, TX 78712, USA
¹¹ HEP Division, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, IL 60439, USA
¹² Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹³ School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne NE17RU, UK
¹⁴ High Energy Physics Division, Argonne National Laboratory, Lemont, IL 60439, USA
¹⁵ Kavli Institute for Particle Astrophysics & Cosmology, PO Box 2450 Stanford University, Stanford, CA 94305, USA
¹⁶ SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
¹⁷ Department of Physics and Astronomy, University of California, One Shields Avenue, Davis, CA 95616, USA

^⋆ Corresponding author: constantin.payerne@gmail.com

Received: 11 February 2025
Accepted: 8 June 2025

Abstract

Context. Cluster scaling relations are key ingredients in cluster abundance-based cosmological studies. In optical cluster cosmology, where clusters are detected through their richness, cluster-weak gravitational lensing has proven to be a powerful tool to constrain the cluster mass-richness relation. This work is conducted as part of the Dark Energy Science Collaboration (DESC), which aims to analyze the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory, starting in 2026.

Aims. Cluster properties inferred from weak lensing, such as mass, suffer from several sources of bias. In this paper, we aim to test the impact of modeling choices and observational systematics in cluster lensing on the inference of the mass-richness relation.

Methods. We constrained the mass-richness relation of 3600 clusters detected by the redMaPPer algorithm in the cosmoDC2 extragalactic mock catalog of the LSST DESC DC2 simulation, covering 440 deg², using number count measurements and either stacked weak lensing profiles or mean cluster masses in several intervals of richness (20 ≤ λ ≤ 200) and redshift (0.2 ≤ z ≤ 1).

Results. We provide the first constraints on the redMaPPer cluster mass-richness relation detected in cosmoDC2. We find that for an LSST-like source galaxy density, our constraints are robust to changes in the concentration-mass relation, as well as the dark matter density profile modeling choices, when source redshifts and shapes are perfectly known. We find that photometric redshift uncertainties can introduce bias at the 1σ level, which could be mitigated by an overall correction factor fitted jointly with the scaling parameters. We find that including positive shear-richness covariance in the fit shifts the results by up to 0.5σ. Our constraints also offer a fair comparison to a fiducial mass-richness relation, obtained from matching cosmoDC2 halo masses to redMaPPer-detected cluster richness results.