Abstract
We present forecasts for the accuracy of determining the parameters of aminimal cosmological model and the total neutrino mass based on combined mockdata for a future Euclid-like galaxy survey and Planck. We considertwo different galaxy surveys: a spectroscopic redshift survey and a cosmicshear survey. We make use of the Monte Carlo Markov Chains (MCMC) technique andassume two sets of theoretical errors. The first error is meant to account foruncertainties in the modelling of the effect of neutrinos on the non-lineargalaxy power spectrum and we assume this error to be fully correlated inFourier space. The second error is meant to parametrize the overall residualuncertainties in modelling the non-linear galaxy power spectrum at smallscales, and is conservatively assumed to be uncorrelated and to increase withthe ratio of a given scale to the scale of non-linearity. It hence increaseswith wavenumber and decreases with redshift. With these two assumptions for theerrors and assuming further conservatively that the uncorrelated error risesabove 2% at k = 0.4 h/Mpc and z = 0.5, we find that a future Euclid-like cosmic shear/galaxy survey achieves a 1-σ error onMν close to 32 meV/25 meV, sufficient for detecting the total neutrinomass with good significance. If the residual uncorrelated errors indeed risesrapidly towards smaller scales in the non-linear regime as we have assumed herethen the data on non-linear scales does not increase the sensitivity to thetotal neutrino mass. Assuming instead a ten times smaller theoretical errorwith the same scale dependence, the error on the total neutrino mass decreasesmoderately from σ(Mν) = 18 meV to 14 meV when mildly non-linearscales with 0.1 h/Mpc < k < 0.6 h/Mpc are included in the analysis of thegalaxy survey data.
Highlights
We present forecasts for the accuracy of determining the parameters of a minimal cosmological model and the total neutrino mass based on combined mock data for a future Euclid-like galaxy survey and Planck
We have presented forecasts of cosmological parameters by using, in combination with Planck data, two Euclid-like mock future data sets: a galaxy spectroscopic redshift survey and a cosmic shear survey
We focused our attention on constraints that can be achieved on the total neutrino mass by using the data in the linear and non-linear regimes
Summary
Throughout this paper, our fiducial model is chosen to be a flat ΛCDM model with three degenerate massive neutrino species. As in most of the recent Fishermatrix-based forecasts, we assume that the reduced data is described by a set of observable power spectra P obs(kref , μ, z), related to the familiar non-linear matter power spectrum PNL(k, z) in a non-trivial way in order to take into account redshift space distortions, linear light-to-mass bias, spectroscopic redshift errors and the Alcock-Paczynsky effect (see A.1) This modeling is imperfect: for this reason we introduce a theoretical error. We assumed that the bias function for each redshift bin could be determined in advance (up to corrections on non-linear scales contained in our global theoretical error). This assumption has been made in most recent forecasts, since both. It seems unlikely that at the time when Euclid data will be analyzed, no information at all will be available on the linear bias of the observed population of galaxies
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