Cluster-void degeneracy breaking: Neutrino properties and dark energy

TL;DR

Future large-scale surveys like Euclid can simultaneously constrain neutrino masses and dark energy properties with high precision by combining cluster and void counts, surpassing current methods.

Contribution

This paper demonstrates that combining cluster and void counts from upcoming surveys can tightly constrain neutrino masses and dark energy parameters, offering a new approach to cosmological parameter estimation.

Findings

Euclid clusters + voids could reach $\sigma(M_ u) \\lesssim 15$ meV

Constraints on $w_0$ and $w_a$ are very tight, e.g., $\\sigma(w_0) \\lesssim 0.02$

Potential to reject inverted neutrino hierarchy at over 99% confidence

Abstract

Future large-scale spectroscopic astronomical surveys, e.g. Euclid, will enable the compilation of vast new catalogues of clusters and voids in the galaxy distribution. By combining the constraining power of both cluster and void number counts, such surveys could place stringent simultaneous limits on the sum of neutrino masses $M_\nu$ and the dark energy equation of state $w(z) = w_0 + w_a z/(1+z)$. For minimal normal-hierarchy neutrino masses, we forecast that Euclid clusters + voids ideally could reach uncertainties $\sigma(M_\nu) \lesssim 15$ meV, $\sigma(w_0) \lesssim~0.02$, $\sigma(w_a) \lesssim 0.07$, independent of other data. Such precision is competitive with expectations for e.g. galaxy clustering and weak lensing in future cosmological surveys, and could reject an inverted neutrino mass hierarchy at $\gtrsim 99\%$ confidence.