Next generation cosmology: constraints from the<i>Euclid</i>galaxy cluster survey

Abstract

We study the characteristics of the galaxy cluster samples expected from the\nEuropean Space Agency's Euclid satellite and forecast constraints on\ncosmological parameters describing a variety of cosmological models. The method\nused in this paper, based on the Fisher Matrix approach, is the same one used\nto provide the constraints presented in the Euclid Red Book (Laureijs et\nal.2011). We describe the analytical approach to compute the selection function\nof the photometric and spectroscopic cluster surveys. Based on the photometric\nselection function, we forecast the constraints on a number of cosmological\nparameter sets corresponding to different extensions of the standard LambdaCDM\nmodel. The dynamical evolution of dark energy will be constrained to Delta\nw_0=0.03 and Delta w_a=0.2 with free curvature Omega_k, resulting in a\n(w_0,w_a) Figure of Merit (FoM) of 291. Including the Planck CMB covariance\nmatrix improves the constraints to Delta w_0=0.02, Delta w_a=0.07 and a\nFoM=802. The amplitude of primordial non-Gaussianity, parametrised by f_NL,\nwill be constrained to \\Delta f_NL ~ 6.6 for the local shape scenario, from\nEuclid clusters alone. Using only Euclid clusters, the growth factor parameter\n\\gamma, which signals deviations from GR, will be constrained to Delta\n\\gamma=0.02, and the neutrino density parameter to Delta Omega_\\nu=0.0013 (or\nDelta \\sum m_\\nu=0.01). We emphasise that knowledge of the observable--mass\nscaling relation will be crucial to constrain cosmological parameters from a\ncluster catalogue. The Euclid mission will have a clear advantage in this\nrespect, thanks to its imaging and spectroscopic capabilities that will enable\ninternal mass calibration from weak lensing and the dynamics of cluster\ngalaxies. This information will be further complemented by wide-area\nmulti-wavelength external cluster surveys that will already be available when\nEuclid flies. [Abridged]\n