# Optical Cluster Cosmology with SDSS redMaPPer clusters and HSC-Y3 lensing measurements

**Authors:** Tomomi Sunayama, Hironao Miyatake, Sunao Sugiyama, Surhud More, Xiangchong Li, Roohi Dalal, Markus Michael Rau, Jingjing Shi, I-Non Chiu, Masato Shirasaki, Tianqing Zhang, Atsushi J. Nishizawa  
**arXiv:** [2309.13025](https://arxiv.org/abs/2309.13025)  
**Date:** 2023-09-22  
**Summary page:** https://www.summarizepaper.com/en/paper/2309.13025v1/

## Key points

- Researchers presented cosmology results from a blind joint analysis of galaxy clusters using data from SDSS redMaPPer cluster catalog and HSC Year3 shape catalog
- Analysis included abundance, clustering, and weak lensing of the galaxy clusters
- Full-forward model developed for cluster observables incorporating empirical modeling for anisotropic boosts on lensing and clustering signals
- Validation done using mock cluster catalogs accounting for observational systematics
- Analysis could robustly constrain cosmological parameters without relying on informative priors
- Cosmological constraints obtained for S8 (σ8 √(Ωm / 0.3)) in flat ΛCDM model with a value of 0.816+0.041-0.039
- Findings consistent with other cosmic microwave background and large-scale structure-based cosmology analyses, including Planck 2018 primary CMB analysis
- Difference in amplitude of lensing signal between SDSS and HSC-Y3 data at larger scales contributed to differences in resulting cosmological constraints
- Comparisons with other cosmology surveys did not show significant tensions with their results

## Summary

In a recent study, researchers presented cosmology results obtained from a blind joint analysis of galaxy clusters using data from the Sloan Digital Sky Survey (SDSS) redMaPPer cluster catalog and the Hyper-Suprime Cam (HSC) Year3 shape catalog. The analysis included the abundance, projected clustering, and weak lensing of the galaxy clusters. The researchers developed a full-forward model for the cluster observables which incorporated empirical modeling for the anisotropic boosts on the lensing and clustering signals of optical clusters. To validate their analysis they used mock cluster catalogs that accounted for observational systematics such as the projection effect and the effect of baryonic feedback. The results showed that their analysis could robustly constrain cosmological parameters in an unbiased manner without relying on informative priors on model parameters. Specifically, when considering the flat ΛCDM model they obtained cosmological constraints for S8 (defined as σ8 √(Ωm / 0.3)), with a value of 0.816+0.041-0.039. Importantly, their findings were consistent with other cosmic microwave background- and large-scale structure-based cosmology analyses including the result from Planck 2018 primary CMB analysis; in fact their S8 value agreed with that from Planck 2018 within 1σ. Further investigation revealed that there was a difference in amplitude of lensing signal measured from SDSS data compared to HSC-Y3 data at larger scales (R > 3 h^−1 Mpc). This discrepancy likely contributed to differences in resulting cosmological constraints between this study and previous work. Comparisons with other cosmology surveys such as Planck 2018 and DES Y3 3x2pt did not show any significant tensions with their results. Overall these findings contribute to our understanding of optical cluster cosmology and provide valuable insights into nature of universe.