Clustering of CODEX clusters
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 Xray (CODEX) sample, in which we take particular care of cluster definition. These clusters were Xray selected using the ROentgen SATellite AllSky Survey and then identified as galaxy clusters using the code redMaPPer run on the photometry of the Sloan Digital Sky Survey. We develop methods for precisely accounting for the sample selection effects on the clustering and demonstrate their robustness using numerical simulations.
Methods: Using the clean CODEX sample, which was obtained by applying a redshiftdependent richness selection, we computed the twopoint autocorrelation function of galaxy clusters in the 0.1 < z < 0.3 and 0.3 < z < 0.5 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 r_{0} = 18.7 ± 1.1 and slope γ = 1.98 ± 0.14 for the correlation function in the full redshift range. By fixing the other cosmological parameters to their nineyear Wilkinson Microwave Anisotropy Probe values, we reproduced the observed shape of the correlation function under the following cosmological conditions: Ω_{m0} = 0.22_{0.03}^{+0.04} and S_{8} = σ_{8}(Ω_{m0}/0.3)^{0.5} = 0.85_{0.08}^{+0.10} with estimated additional systematic errors of σ_{Ωm0} = 0.02 and σ_{S8} = 0.20. We illustrate the complementarity of clustering constraints by combining them with CODEX cosmological constraints based on the Xray luminosity function, deriving Ω_{m0} = 0.25 ± 0.01 and σ_{8} = 0.81_{0.02}^{+0.01} with an estimated additional systematic error of σ_{Ωm0} = 0.07 and σ_{σ8} = 0.04. The mass calibration and statistical quality of the mass tracers are the dominant source of uncertainty.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 February 2021
 DOI:
 10.1051/00046361/202038807
 arXiv:
 arXiv:2012.00090
 Bibcode:
 2021A&A...646A...8L
 Keywords:

 largescale structure of Universe;
 cosmology: observations;
 galaxies: clusters: general;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 13 pages, 15 figures