Richness-based masses of rich and famous galaxy clusters

Abstract

We present a catalog of galaxy cluster masses derived by exploiting the tight correlation between mass and richness, i.e., a properly computed number of bright cluster galaxies. The richness definition adopted in this work is properly calibrated, shows a small scatter with mass, and has a known evolution, which means that we can estimate accurate (0.16 dex) masses more precisely than by adopting any other richness estimates or X-ray or SZ-based proxies based on survey data. We measured a few hundred galaxy clusters at 0.05 < z < 0.22 in the low-extinction part of the Sloan Digital Sky Survey footprint that are in the 2015 catalog of Planck-detected clusters, that have a known X-ray emission, that are in the Abell catalog, or that are among the most most cited in the literature. Diagnostic plots and direct images of clusters are individually inspected and we improved cluster centers and, when needed, we revised redshifts. Whenever possible, we also checked for indications of contamination from other clusters on the line of sight, and found ten such cases. All this information, with the derived cluster mass values, are included in the distributed value-added cluster catalog of the 275 clusters with a derived mass larger than 10 14 M . Finally, in a technical appendix we illustrate with Planck clusters how to minimize the sensitivity of comparisons between masses listed in different catalogs to the specific overlapping of the considerd subsamples, a problem recognized but not solved in the literature.

Cluster richness–mass calibration with cosmic microwave background lensing

“…However, a perrennial problem has been the mapping of optical 'richness' measurements on to total cluster mass. 3,[9][10][11][12] Emitted at a conformal distance of 14 gigaparsecs, the cosmic microwave background acts as a backlight to all intervening mass in the Universe, and therefore has been gravitationally lensed. [13][14][15] Here we present a calibration of cluster optical richness at the 10 per cent level by measuring the average cosmic microwave background lensing convergence measured by Planck towards the positions of large numbers of optically-selected clusters, detecting the deflection of photons by haloes of total mass of the order 10 14 M .…”

Searching for galaxy clusters in the Kilo-Degree Survey

“…5 was based on an X-ray selected sample of 39 clusters with masses derived by the caustics technique (Rines et al 2013). An extended catalog of 275 clusters with richness-based masses was presented in Andreon (2016). Since these clusters are not covered by the KDR2 tiles and no similar sample is yet available for the current KiDS area, we proceeded as follows.…”

Precise clustering and density evolution of redMaPPer galaxy clusters versus MXXL simulation

“…Undermining the use of clusters in such comparisons is the indirectness of cluster mass estimates for which empirical scaling relations have to be relied on for converting observables to mass. Cluster richness seems to provide a robust connection as it is close to being linearly related to mass (Rozo et al 2009a,b;Rykoff et al 2012), with a slope of d log M200/d log N ≃ 1.1, and a ≃ 20% inherent scatter inferred (Andreon 2016) and with little evidence of evolution (Younger et al 2005;Andreon & Congdon 2014;Hennig et al 2016). Power-law scalings to convert X-ray and SZ measurements to total cluster masses are complicated by compressed gas and shocks from cluster interactions, so that the selection function and its evolution is challenging (Suto et al 2000;Allen et al 2011;Mroczkowski et al 2012;Molnar & Broadhurst 2015;Sereno et al 2015a;Andreon et al 2016).…”