Next generation cosmology: constraints from theEuclidgalaxy cluster survey

Abstract

We study the characteristics of the galaxy cluster samples expected from the European Space Agency's Euclid satellite and forecast constraints on parameters describing a variety of cosmological models. The method used in this paper, based on the Fisher Matrix approach, is the same one used to provide the constraints presented in the Euclid Red Book (Laureijs et al. 2011). We describe the analytical approach to compute the selection function of the photometric and spectroscopic cluster surveys. Based on the photometric selection function, we forecast the constraints on a number of cosmological parameter sets corresponding to different extensions of the standard ΛCDM model, including a redshift-dependent Equation of State for Dark Energy, primordial non-Gaussianity, modified gravity and non-vanishing neutrino masses. Our results show that Euclid clusters will be extremely powerful in constraining the amplitude of the matter power spectrum σ 8 and the mass density parameter Ω m . The dynamical evolution of dark energy will be constrained to ∆w 0 = 0.03 and ∆w a = 0.2 with free curvature Ω k , resulting in a (w 0 , w a ) Figure of Merit (FoM) of 291. Including the Planck CMB covariance matrix, thereby information on the geometry of the universe, improves the constraints to ∆w 0 = 0.02, ∆w a = 0.07 and a FoM= 802. The amplitude of primordial nonGaussianity, parametrised by f NL , will be constrained to ∆ f NL ≃ 6.6 for the local shape scenario, from Euclid clusters alone. Using only Euclid clusters, the growth factor parameter γ, which signals deviations from General Relativity, will be constrained to ∆γ = 0.02, and the neutrino density parameter to ∆Ω ν = 0.0013 (or ∆ m ν = 0.01). We emphasise that knowledge of the observable-mass scaling relation will be crucial to constrain cosmological parameters from a cluster catalogue. The Euclid mission will have a clear advantage in this respect, thanks to its imaging and spectroscopic capabilities that will enable internal mass calibration from weak lensing and the dynamics of cluster galaxies. This information will be further complemented by wide-area multi-wavelength external cluster surveys that will already be available when Euclid flies. c 0000 RAS 2 B. Sartoris et al.

Velocity segregation effects in galaxy clusters at 0.4 ≲z≲ 1.5

“…This result has interesting implications for the cosmological application of the velocity dispersion measurements that the Euclid satellite will make, possible by targeting Hα-emitting star-forming galaxies in its spectroscopic survey (e.g. Laureijs et al 2011;Sartoris et al 2016). Notes.…”

Cluster–void Degeneracy Breaking: Dark Energy, Planck, and the Largest Cluster and Void

“…Clusters are growth-sensitive for  z 0.5 (Levine et al 2002). Voids form slower, and are therefore sensitive to perturbation growth at low redshifts: for shell- Figure 4 in Sartoris et al 2015 andFigures 4 and6 in Pisani et al 2015).…”

The universality of the virial halo mass function and models for non-universality of other halo definitions

“…One of the most important application that necessite of an accurate and well calibrated mass function is the study of the observed cluster counts (Vikhlinin et al 2009;Rozo et al 2010;Planck Collaboration et al 2013a;Sartoris et al 2015). Degeneracies between fitted parameters mean that the best fit parameters to fits restricted to cluster mass halos (M 10 1 3h −1 M ) may differ from those returned from fitting a larger range of masses (we refer to these as the CMF and HMF, for cluster and halo mass functions, respectively).…”

“…For an extensive review, see Borgani & Kravtsov (2011). However in the near future, many wide-field surveys are expected to use the cluster mass function to constrain cosmological parameters (Pillepich et al 2012;Laureijs et al 2011;Sartoris et al 2015;Boldrin et al 2015). In the light of these, a mass function calibrated to an accuracy of a few percent, and flexible enough to account for different halo identification definitions, is of primary importance.…”