The extended ROSAT-ESO Flux-Limited X-ray Galaxy Cluster Survey (REFLEX II) VI. Effect of massive neutrinos on the cosmological constraints from clusters

TL;DR

This study investigates how including massive neutrinos affects cosmological constraints derived from galaxy cluster data, finding that neutrino masses around 0.45 eV can reconcile discrepancies with Planck CMB results.

Contribution

It extends previous cluster-based cosmological analyses by incorporating massive neutrinos, providing new constraints on neutrino mass and its impact on large-scale structure.

Findings

Neutrino masses up to 0.6 eV have a weak effect on Omega_m and sigma_8 constraints.

Neutrino mass around 0.45 eV can resolve tension between cluster data and Planck results.

Cluster data, combined with other large-scale structure measurements, can effectively constrain total neutrino mass.

Abstract

Clusters of galaxies are important probes for the large-scale structure that allow us to test cosmological models. With the REFLEX II galaxy cluster survey we previously derived tight constraints on the cosmological parameters for the matter density, Omega_m, and the amplitude parameter of the matter density fluctuations, sigma_8. Whereas in these previous studies no effect of massive neutrinos was taken into account, we explore these effects in the present publication. We derive cosmological constraints for the sum of the neutrino masses of the conventional three neutrino families in the range 0 to 0.6 eV. The influence on the constraints of Omega_m and sigma_8 for the expected mass range is weak. Interesting constraints on the neutrino properties can be derived by comparing the cluster data with those from the Planck cosmic microwave background observations. The current tension between the Planck results and clusters can formally be resolved with neutrino masses of about M_nu = 0.45 (+- 0.28, 1-sigma) eV. While we caution not to consider this a firm measurement because it might also be the result of unresolved systematics, it is interesting that other measurements of the local large-scale structure fluctuation amplitude, like that of cosmic lensing shear, yield similar results and additionally confirm the effect of massive neutrinos. Among the indicators for massive neutrinos, galaxy clusters and in particular our large and well-controlled cluster survey currently provide the best potential for constraints of the total neutrino mass.