Brightest X-ray clusters of galaxies in the CFHTLS wide fields: Catalog and optical mass estimator

TL;DR

This paper presents a new optical mass proxy and automated identification algorithms for X-ray galaxy clusters in the CFHTLS, demonstrating high accuracy and low scatter in mass estimates, and providing extensive cluster catalogs.

Contribution

Introduction of a new optical mass proxy based on the red sequence and automated algorithms for identifying X-ray clusters in CFHTLS data.

Findings

Red sequence luminosity correlates with X-ray luminosity with 0.20 dex scatter.

Automated algorithms identify 100% of significant X-ray clusters.

Catalogs of 196 and 32 clusters from XMM and RASS data, respectively.

Abstract

The CFHTLS presents a unique data set for weak lensing studies, having high quality imaging and deep multi-band photometry. We have initiated an XMM-CFHTLS project to provide X-ray observations of the brightest X-ray selected clusters within the wide CFHTLS area. Performance of these observations and the high quality of CFHTLS data, allows us to revisit the identification of X-ray sources, introducing automated reproducible algorithms, based on the multi-color red sequence finder. We have also introduced a new optical mass proxy. We provide the calibration of the red sequence observed in the CFHT filters and compare the results with the traditional single color red sequence and photoz. We test the identification algorithm on the subset of highly significant XMM clusters and identify 100% of the sample. We find that the integrated z-band luminosity of the red sequence galaxies correlates well with the X-ray luminosity with a surprisingly small scatter of 0.20 dex. We further use the multi-color red sequence to reduce spurious detections in the full XMM and RASS data sets, resulting in catalogs of 196 and 32 clusters, respectively. We made spectroscopic follow-up observations of some of these systems with HECTOSPEC and in combination with BOSS DR9 data. We also describe the modifications needed to the source detection algorithm in order to keep high purity of extended sources in the shallow X-ray data. We also present the scaling relation between X-ray luminosity and velocity dispersion.