The Next Generation Virgo Cluster Survey. XX. RedGOLD Background Galaxy Cluster Detections

Abstract

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 ($\sim 20de{g}^2$), and the other using four bandpasses ($u^{\ast },g,i,z$) for the entire NGVS area. Based on our previous CFHT-LS W1 studies, we estimate that both of our catalogs are $\sim 100\%$($\sim 70\%$) complete and $\sim 80\%$ pure, at $z\le 0.6$($z\lesssim 1$), for galaxy clusters with masses of $M\gtrsim 10^{14}{M}_{\odot }$. 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 $\sim 40\%$ lower at $0.5\le z<0.6$ and $\sim 20\%$ 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 $\sim 90-100\%$ of its detections.

Licitra e al. 2016, ApJ, 829, 44 Our catalogs are planned to be available on ADS