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$deg^2$ of the Virgo cluster in the $u^*,g,r,i,z$-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 ($\sim 20 \
deg^2$), and the other using four bandpasses ($u^*,g,i,z$) for the entire NGVS
area. Based on our previous CFHT-LS W1 studies, we estimate that both of our
catalogs are $\sim100\%$($\sim70\%$) complete and $\sim80\%$ pure, at $z\le
0.6$($z\lesssim1$), for galaxy clusters with masses of $M\gtrsim10^{14}\
M_{\odot}$. 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
$\sim40\%$ lower at $0.5\le z<0.6$ and $\sim20\%$ 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 $M_{500} > 1.4 \times 10^{14} \rm M_{\odot}$ 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 $\sim 90-100\%$ of its detections.
