Euclid preparation XXVII Covariance model validation for the 2-point correlation function of galaxy clusters by Euclid Collaboration et al. on Friday 25 November

Aims. We validate a semi-analytical model for the covariance of real-space

2-point correlation function of galaxy clusters. Methods. Using 1000 PINOCCHIO

light cones mimicking the expected Euclid sample of galaxy clusters, we

calibrate a simple model to accurately describe the clustering covariance.

Then, we use such a model to quantify the likelihood analysis response to

variations of the covariance, and investigate the impact of a

cosmology-dependent matrix at the level of statistics expected for the Euclid

survey of galaxy clusters. Results. We find that a Gaussian model with

Poissonian shot-noise does not correctly predict the covariance of the 2-point

correlation function of galaxy clusters. By introducing few additional

parameters fitted from simulations, the proposed model reproduces the numerical

covariance with 10 per cent accuracy, with differences of about 5 per cent on

the figure of merit of the cosmological parameters $\Omega_{\rm m}$ and

$\sigma_8$. Also, we find that the cosmology-dependence of the covariance adds

valuable information that is not contained in the mean value, significantly

improving the constraining power of cluster clustering. Finally, we find that

the cosmological figure of merit can be further improved by taking mass binning

into account. Our results have significant implications for the derivation of

cosmological constraints from the 2-point clustering statistics of the Euclid

survey of galaxy clusters.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12965v1