THE NEXT GENERATION VIRGO CLUSTER SURVEY. XX. RedGOLD BACKGROUND GALAXY CLUSTER DETECTIONS

We build a background cluster candidate catalog from the Next Generation Virgo Cluster Survey (NGVS) using our detection algorithm RedGOLD. The NGVS covers 104 deg^2 of the Virgo cluster in the u*, g, r, i, z-bandpasses to a depth of g ~ 25.7 mag (5σ). Part of the survey was not covered or has shallow observations in the r band. We build two cluster catalogs: one using all bandpasses, for the fields with deep r-band observations (~20 deg^2), and the other using four bandpasses (u*, g, i, z) for the entire NGVS area. Based on our previous Canada–France–Hawaii Telescope Legacy Survey W1 studies, we estimate that both of our catalogs are ~100% (~70%) complete and ~80% pure, at z ≤ 0.6 (z ≾1), for galaxy clusters with masses of M ≳ 10^(14) M⊙. We show that when using four bandpasses, though the photometric redshift accuracy is lower, RedGOLD detects massive galaxy clusters up to z ~ 1 with completeness and purity similar to the five-band case. This is achieved when taking into account the bias in the richness estimation, which is ~40% lower at 0.5 ≤ z 1.4 × 10^(14) M⊙ and 0.08 < z < 0.5. Because of our different cluster richness limits and the NGVS depth, our catalogs reach lower masses than the published redMaPPer cluster catalog over the area, and we recover ~90%–100% of its detections.