The HectoMAP Cluster Survey. I. redMaPPer Clusters

Abstract

We use the dense HectoMAP redshift survey to explore the properties of 104 redMaPPer cluster candidates. The redMaPPer systems in HectoMAP cover the full range of richness and redshift (0.08 < z < 0.60). Fifteen of the systems included in the Subaru /Hyper Suprime-Cam public data release are bona fide clusters. The median number of spectroscopic members per cluster is ∼20. We include redshifts of 3547 member candidates listed in the redMaPPer catalog whether they are cluster members or not. We evaluate the redMaPPer membership probability spectroscopically. The purity (number of real systems) in redMaPPer exceeds 90% even at the lowest richness. Three massive galaxy clusters ( M ∼ 2 × 10 13 M ⊙ ) associated with X-ray emission in the HectoMAP region are not included in the public redMaPPer catalog with λ rich  > 20, because they lie outside the cuts for this catalog.