Model marginalized constraints on neutrino properties from cosmology

Abstract

We present robust, model-marginalized limits on both the total neutrino mass ( mν ) and abundances (N eff ) to minimize the role of parameterizations, priors and models when extracting neutrino properties from cosmology. The cosmological observations we consider are Cosmic Microwave Background temperature fluctuation and polarization measurements, Supernovae Ia luminosity distances, Baryon Acoustic Oscillation observations and determinations of the growth rate parameter from the Data Release 16 of the Sloan Digital Sky Survey IV. The degenerate neutrino mass spectrum (which implies the prior mν > 0) is weakly (moderately) preferred over the normal and inverted hierarchy possibilities, which imply the priors mν > 0.06 and mν > 0.1 eV respectively. Concerning the underlying cosmological model, the ΛCDM minimal scenario is almost always strongly preferred over the possible extensions explored here. The most constraining 95% CL bound on the total neutrino mass in the ΛCDM+ mν picture is mν < 0.087 eV. The parameter N eff is restricted to 3.08 ± 0.17 (68% CL) in the ΛCDM+N eff model. These limits barely change when considering the ΛCDM+ mν + N eff scenario. Given the robustness and the strong constraining power of the cosmological measurements employed here, the model-marginalized posteriors obtained considering a large spectra of non-minimal cosmologies are very close to the previous bounds, obtained within the ΛCDM framework in the degenerate neutrino mass spectrum. Future cosmological measurements may improve the current Bayesian evidence favouring the degenerate neutrino mass spectra, challenging therefore the consistency between cosmological neutrino mass bounds and oscillation neutrino measurements, and potentially suggesting a more complicated cosmological model and/or neutrino sector.