Measuring the neutrino mass from future wide galaxy cluster catalogues

TL;DR

The paper forecasts how a Euclid-like photometric galaxy cluster catalogue can constrain the total neutrino mass $M_\nu$ by combining cluster counts with the BAO and shape information of the cluster power spectrum, while marginalising over mass–observable uncertainties and using Planck priors. Using a Fisher matrix framework, it demonstrates that joint analysis greatly enhances parameter constraints compared with each probe alone, with $\sigma(M_\nu)$ dropping from the order of ~eV in general cosmologies to ~0.08–0.04 eV under a flat $\Lambda$CDM model. The authors show that mass-calibration improvements (i.e., fixing nuisance parameters) can further reduce $\sigma(M_\nu)$ to the $\sim0.01$–$0.04$ eV level, potentially allowing a detection of the minimum neutrino mass. Overall, the work highlights that Euclid-like cluster surveys, particularly when paired with Planck CMB priors, offer a powerful avenue for neutrino-mass measurements and for constraining dark energy dynamics, contingent on controlling systematics and mass calibration.

Abstract

We present forecast errors on a wide range of cosmological parameters obtained from a photometric cluster catalogue of a future wide-field Euclid-like survey. We focus in particular on the total neutrino mass as constrained by a combination of the galaxy cluster number counts and correlation function. For the latter we consider only the shape information and the Baryon Acoustic Oscillations (BAO), while marginalising over the spectral amplitude and the redshift space distortions. In addition to the cosmological parameters of the standard LCDM+nu model we also consider a non-vanishing curvature, and two parameters describing a redshift evolution for the dark energy equation of state. For completeness, we also marginalise over a set of "nuisance" parameters, representing the uncertainties on the cluster mass determination. We find that combining cluster counts with power spectrum information greatly improves the constraining power of each probe taken individually, with errors on cosmological parameters being reduced by up to an order of magnitude. In particular, the best improvements are for the parameters defining the dynamical evolution of dark energy, where cluster counts break degeneracies. Moreover, the resulting error on neutrino mass is at the level of σ(M_ν)\sim 0.9 eV, comparable with that derived from present Ly-alpha forest measurements and Cosmic Microwave background (CMB) data in the framework of a non-flat Universe. Further adopting Planck priors and reducing the number of free parameters to a LCDM+nu cosmology allows to place constraints on the total neutrino mass of σ(M_ν) \sim 0.08 eV, close to the lower bound enforced by neutrino oscillation experiments. [abridged]

Figures (2)

• Figure 1: 2-parameter projected $68\%$ C.L. contours in the $M_\nu$-$q_\alpha$ subspace with $q_\alpha=\Omega_m,\,\Omega_K,\,\Omega_b,\,h$. The solid black line and the dotted blue line correspond to BAO+$P_{\rm c}(k)$-shape cluster data from a Euclid-like survey in combination with Planck priors for a general cosmology, and a $\Lambda$CDM Universe, respectively. The dashed red line, and the dot-dashed orange line are obtained with the further addition of cluster counts data, and represent the confidence contours obtained for the two cosmological models, respectively.
• Figure 2: 2-parameter projected $68\%$ C.L. contours in the $M_\nu$-$q_\alpha$ subspace with $q_\alpha=n_s,\,w_0,\,w_a,\,\log(10^{10}A_s)$. The solid black line and the dotted blue line correspond to BAO+$P_{\rm c}(k)$-shape cluster data from a Euclid-like survey in combination with Planck priors for a general cosmology, and a $\Lambda$CDM Universe, respectively. The dashed red line, and the dot-dashed orange line are obtained with the further addition of cluster counts data, and represent the confidence contours obtained for the two cosmological models, respectively.