Galaxy clusters identified from the SDSS DR6 and their properties

TL;DR

This paper presents a large catalog of nearly 40,000 galaxy clusters identified from SDSS DR6 data, extending to higher redshifts than previous catalogs, with detailed properties and new X-ray cluster candidates.

Contribution

The study introduces a new method for identifying galaxy clusters using SDSS DR6 photometric redshifts, expanding the redshift range and providing detailed cluster properties and new X-ray candidates.

Findings

Identified 39,668 galaxy clusters in 0.05<z<0.6 with high completeness and low contamination.

Cluster mass correlates strongly with richness and luminosity, following specific power laws.

Discovered 685 new X-ray cluster candidates through cross-identification with ROSAT data.

Abstract

Clusters of galaxies in most previous catalogs have redshifts z<0.3. Using the photometric redshifts of galaxies from the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we identify 39,668 clusters in the redshift range 0.05< z <0.6 with more than eight luminous (M_r<-21) member galaxies. Cluster redshifts are estimated accurately with an uncertainty less than 0.022. The contamination rate of member galaxies is found to be roughly 20%, and the completeness of member galaxy detection reaches to ~90%. Monte Carlo simulations show that the cluster detection rate is more than 90% for massive (M_{200}>2\times10^{14} M_{\odot}) clusters of z<0.42. The false detection rate is ~5%. We obtain the richness, the summed luminosity, and the gross galaxy number within the determined radius for identified clusters. They are tightly related to the X-ray luminosity and temperature of clusters. Cluster mass is related to the richness and summed luminosity with M_{200}\propto R^{1.90\pm0.04} and M_{200}\propto L_r^{1.64\pm0.03}, respectively. In addition, 685 new candidates of X-ray clusters are found by cross-identification of our clusters with the source list of the ROSAT X-ray survey.