Velocity Dispersions of Clusters in the Dark Energy Survey Y3 redMaPPer Catalog

Abstract

We measure the velocity dispersions of clusters of galaxies selected by the redMaPPer algorithm in the first three years of data from the Dark Energy Survey (DES), allowing us to probe cluster selection and richness estimation, $\lambda$, in light of cluster dynamics. Our sample consists of 126 clusters with sufficient spectroscopy for individual velocity dispersion estimates. We examine the correlations between cluster velocity dispersion, richness, X-ray temperature and luminosity as well as central galaxy velocity offsets. The velocity dispersion-richness relation exhibits a bimodal distribution. The majority of clusters follow scaling relations between velocity dispersion, richness, and X-ray properties similar to those found for previous samples; however, there is a significant population of clusters with velocity dispersions which are high for their richness. These clusters account for roughly 22\% of the $\lambda <70$ systems in our sample, but more than half (55\%) of $\lambda <70$ clusters at $z>0.5$. A couple of these systems are hot and X-ray bright as expected for massive clusters with richnesses that appear to have been underestimated, but most appear to have high velocity dispersions for their X-ray properties likely due to line-of-sight structure. These results suggest that projection effects contribute significantly to redMaPPer selection, particularly at higher redshifts and lower richnesses. The redMaPPer determined richnesses for the velocity dispersion outliers are consistent with their X-ray properties, but several are X-ray undetected and deeper data is needed to understand their nature.

22 pages, accepted to MNRAS

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Cited by in corpus (12)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• The Three Hundred project: Galaxy groups do not survive cluster infall
• The XMM Cluster Survey analysis of the SDSS DR8 redMaPPer Catalogue: Implications for scatter, selection bias, and isotropy in cluster scaling relations
• MCXC-II: Second release of the Meta-Catalogue of X-Ray detected Clusters of galaxies
• Optical galaxy cluster mock catalogs with realistic projection effects: Validations with the SDSS clusters
• Modelling the selection of galaxy groups with end to end simulations
• Satellite Content and Halo Mass of Galaxy Clusters: Comparison between Red-Sequence and Halo-based Optical Cluster Finders
• Improving Galaxy Cluster Selection with the Outskirt Stellar Mass of Galaxies
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• Selection Function of Clusters in Dark Energy Survey Year 3 Data from Cross-Matching with South Pole Telescope Detections
• Dark Energy Survey Year 3 Results: Mis-centering calibration and X-ray-richness scaling relations in redMaPPer clusters
• Estimating the Masses of Supercluster-Scale Filaments from Redshift Dispersions