We present the RASS-MCMF catalogue of 8449 X-ray selected galaxy clusters over 25000deg^2^ of extragalactic sky. The accumulation of deep multiband optical imaging data, the development of the Multi-Component Matched Filter (MCMF) cluster confirmation algorithm, and the release of the DESI Legacy Survey DR10 catalogue makes it possible - for the first time, more than 30yr after the launch of the ROSAT X-ray satellite - to identify the majority of the galaxy clusters detected in the second ROSAT All-Sky-Survey (RASS) source catalogue (2RXS). The resulting 90 per cent pure RASS-MCMF catalogue is the largest intracluster medium (ICM)-selected cluster sample to date. RASS-MCMF probes a large dynamic range in cluster mass spanning from galaxy groups to the most massive clusters. The cluster redshift distribution peaks at z~0.1 and extends to redshifts z~1. Out to z~0.4, the RASS-MCMF sample contains more clusters per redshift interval (dN/dz) than any other ICM-selected sample. In addition to the main sample, we present two subsamples with 6912 and 5506 clusters, exhibiting 95 per cent and 99 per cent purity, respectively. We forecast the utility of the sample for a cluster cosmological study, using realistic mock catalogues that incorporate most observational effects, including the X-ray exposure time and background variations, the existence likelihood selection and the impact of the optical cleaning with the algorithm MCMF. Using realistic priors on the observable-mass relation parameters from a DES-based weak lensing analysis, we estimate the constraining power of the RASS-MCMFxDES sample to be of 0.026, 0.033, and 0.15 (1{sigma}) on the parameters {OMETA}m, {sigma}8, and w, respectively.

Cone search capability for table J/MNRAS/526/3757/catalog (RASS-MCMF catalogue)