The RedGOLD Cluster Detection Algorithm and its Cluster Candidate Catalogue for the CFHT-LS W1

TL;DR

RedGOLD is a new cluster detection algorithm that identifies galaxy overdensities with high purity and completeness, and provides a detailed catalog for the CFHT-LS W1 field, improving upon previous methods in accuracy and reliability.

Contribution

The paper introduces the RedGOLD algorithm, optimizing cluster detection parameters using simulations and X-ray data, resulting in a high-purity, high-completeness galaxy cluster catalog for CFHT-LS W1.

Findings

Achieves ~80% purity up to z~1

Detects 11 clusters per deg^2 up to z~1.1

Recovers 93% of redMaPPer clusters with better redshift accuracy

Abstract

RedGOLD searches for red-sequence galaxy overdensities while minimizing contamination from dusty star-forming galaxies. It imposes an NFW profile and calculates cluster detection significance and richness. We optimize these latter two parameters using both simulations and X-ray detected cluster catalogs, and obtain a catalog $\sim 80\%$ pure up to $z \sim 1$, and $\sim 100\%$ ($\sim 70\%$) complete at $z\le 0.6$ ( $z\lesssim1$) for galaxy clusters with $M \gtrsim 10^{14}\ {\rm M_{\odot}}$ at the CFHT-LS Wide depth. In the CFHT-LS W1, we detect 11 cluster candidates per $\rm deg^2$ out to $z\sim1.1$. When we optimize both completeness and purity, RedGOLD obtains a cluster catalog with higher completeness and purity than other public catalogs, obtained using CFHT-LS W1 observations, for $M \gtrsim 10^{14}\ {\rm M_{\odot}}$. We use X-ray detected cluster samples to extend the study of the X-ray temperature-optical richness relation to a lower mass threshold, and find a mass scatter at fixed richness of $\sigma_{lnM|\lambda}=0.39\pm0.07$ and $\sigma_{lnM|\lambda}=0.30\pm0.13$ for the Gozaliasl et al. (2014) and Mehrtens et al. (2012) samples. When considering similar mass ranges as previous work, we recover a smaller scatter in mass at fixed richness. We recover $93\%$ of the redMaPPer detections, and find that its richness estimates is on average $\sim 40-50\%$ larger than ours at $z>0.3$. RedGOLD recovers X-ray cluster spectroscopic redshifts at better than $5\%$ up to $z\sim1$, and the centers within a few tens of arcseconds.