Clustering of CODEX clusters
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Date
2021
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Abstract
Context. The clustering of galaxy clusters links the spatial nonuniformity of dark matter halos to the growth of the primordial spectrum of perturbations. The amplitude of the clustering signal is widely used to estimate the halo mass of astrophysical objects. The advent of cluster mass calibrations enables using clustering in cosmological studies. Aims. We analyze the autocorrelation function of a large contiguous sample of galaxy clusters, the Constrain Dark Energy with X-ray (CODEX) sample, in which we take particular care of cluster definition. These clusters were X-ray selected using the ROentgen SATellite (ROSAT) All-Sky Survey (RASS) and then identified as galaxy clusters using the code redMaPPer run on the photometry of the Sloan Digital Sky Survey (SDSS). We develop methods for precisely accounting for the sample selection e ects on the clustering and demonstrate their robustness using numerical simulations. Methods. Using the clean CODEX sample, which was obtained by applying a redshift-dependent richness selection, we computed the two-point autocorrelation function of galaxy clusters in the 01 < z < 03 and 03 < z < 05 redshift bins. We compared the bias in the measured correlation function with values obtained in numerical simulations using a similar cluster mass range. Results. By fitting a power law, we measured a correlation length r0 = 187 11 and slope = 198 014 for the correlation function in the full redshift range. By fixing the other cosmological parameters to their nine-year Wilkinson Microwave Anisotropy Probe (WMAP) values, we reproduced the observed shape of the correlation function under the following cosmological conditions: m0 = 022+004 003 and S8 = 8( m0 03)05 = 085+010 008 with estimated additional systematic errors of m0 = 002 and S8 = 020.We illustrate the complementarity of clustering constraints by combining them with CODEX cosmological constraints based on the X-ray luminosity function, deriving m0 = 025 001 and 8 = 081+001 002 with an estimated additional systematic error of 8 = 004. The mass calibration and statistical quality of the mass tracers are the dominant source of uncertainty.
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large-scale structure of Universe, cosmology: observations, galaxies: clusters: general