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, using our detection algorithm RedGOLD. The NGVS covers 104$de{g}^2$ of the Virgo cluster in the $u^{\ast },g,r,i,z$-bandpasses to a depth of $g\sim 25.7$~mag (5$\sigma$). 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 ($\sim 20
deg^2$),andtheotherusingfourbandpasses($u^*,g,i,z$) for the entire NGVS area. Based on our previous CFHT-LS W1 studies, we estimate that both of our catalogs are $\sim 100\mathrm{\%}$($\sim 70\mathrm{\%}$) complete and $\sim 80\mathrm{\%}$ pure, at $z\le 0.6$($z\lesssim1$),forgalaxyclusterswithmassesof$M\gtrsim10^{14}
M_{\odot}$. We show that when using four bandpasses, though the photometric redshift accuracy is lower, RedGOLD detects massive galaxy clusters up to $z\sim 1$ 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 $\sim 40\mathrm{\%}$ lower at $0.5\le z<0.6$ and $\sim 20\mathrm{\%}$ higher at $0.6<z<0.8$, with respect to the five-band case. RedGOLD recovers all the X-ray clusters in the area with mass $M_{500}>1.4\times {10}^{14}{\mathrm{M}}_{\odot }$ and $0.08<z<0.5$. Because of our different cluster richness limits and the NGVS depth, our catalogs reach to lower masses than the published redMaPPer cluster catalog over the area, and we recover $\sim 90-100\mathrm{\%}$ of its detections.