Cosmological constraints on the neutrino mass including systematic uncertainties

TL;DR

The paper tackles how systematic uncertainties propagate into cosmological constraints on the neutrino mass sum $Σm_ν$ within an extended ΛCDM framework, adopting a 3ν degenerate-mass model guided by oscillation data. It performs a rigorous, data-driven comparison of Planck high-ℓ likelihoods with differing foreground treatments, examines low-ℓ handling and CMB lensing, and combines CMB with BAO and SN data to quantify degeneracies and derive a robust upper bound. Using profile likelihoods and incorporating Planck lensing and updated τ_reio constraints, the authors obtain a final bound of $Σm_ν < 0.17$ eV at 95% CL, with an estimated foreground-systematics contribution of about 0.01 eV, and show no preference for NH vs IH given current data. The work highlights the critical role of foreground modelling and lensing data in deriving robust neutrino-mass limits and underscores the need for careful propagation of systematics in precision cosmology, with implications for future Stage-4 CMB and galaxy surveys.

Abstract

When combining cosmological and oscillations results to constrain the neutrino sector, the question of the propagation of systematic uncertainties is often raised. We address this issue in the context of the derivation of an upper bound on the sum of the neutrino masses ($Σm_ν$) with recent cosmological data. This work is performed within the ${\mathrm{Λ{CDM}}}$ model extended to $Σm_ν$, for which we advocate the use of three mass-degenerate neutrinos. We focus on the study of systematic uncertainties linked to the foregrounds modelling in CMB data analysis, and on the impact of the present knowledge of the reionisation optical depth. This is done through the use of different likelihoods built from Planck data. Limits on $Σm_ν$ are derived with various combinations of data, including the latest Baryon Acoustic Oscillations (BAO) and Type Ia Supernovae (SN) results. We also discuss the impact of the preference for current CMB data for amplitudes of the gravitational lensing distortions higher than expected within the ${\mathrm{Λ{CDM}}}$ model, and add the Planck CMB lensing. We then derive a robust upper limit: $Σm_ν< 0.17\hbox{ eV at }95\% \hbox{CL}$, including 0.01 eV of foreground systematics. We also discuss the neutrino mass repartition and show that today's data do not allow one to disentangle normal from inverted hierarchy. The impact on the other cosmological parameters is also reported, for different assumptions on the neutrino mass repartition, and different high and low multipole CMB likelihoods.

Figures (1)

• Figure 1: Individual neutrino masses as a function of $\mathrm{\Sigma m_{\nu}}$ for the two hierarchies (NH : plain line, IH dotted lines), under the assumptions given by equations \ref{['eq:dm12']} and \ref{['eq:dm13']}-\ref{['eq:dm13ih']}. The vertical dahed lines outline the minimal $\mathrm{\Sigma m_{\nu}}$ value allowed in each case (corresponding to one massless neutrino generation). The log vertical axis prevents from the difference between $m_1$ and $m_2$ to be resolved in IH.