Cosmological Preference for a Positive Neutrino Mass at 2.7$σ$: A Joint Analysis of DESI DR2, DESY5, and DESY1 Data

Abstract

Neutrinos and dark energy (DE) have entered a new era of investigation, as the latest DESI baryon acoustic oscillation measurements tighten the constraints on the neutrino mass and suggest that DE may be dynamical rather than a cosmological constant. {In this work, we obtain a high-confidence measurement of the neutrino mass within a dynamical DE framework. A joint analysis of DESI DR2, cosmic microwave background, DESY5 supernova, and DESY1 weak lensing data yields a total neutrino mass of $\sum m_ν= 0.098^{+0.016}_{-0.037}\,\mathrm{eV}$, indicating a measurement for a non-zero, positive neutrino mass at the $2.7σ$ level within the $w_0w_a$CDM framework. This high-confidence measurement is driven mainly by these factors: (i) the DESI's preference for a dynamical DE with its equation of state evolving from $w< -1$ at early times to $w> -1$ at late times, thus leading to a larger neutrino mass; (ii) treating $N_{\mathrm{eff}}$ as a free parameter together with the inclusion of weak lensing data, which likewise allows for an increased neutrino mass.} In future, even higher-confidence measurements of neutrino mass are expected with stronger preferences for dynamical DE in light of more complete DESI data releases.

Figures (4)

• Figure 1: The marginalized 1D posterior distributions on $\sum m_{\nu}$ using DESI, CMB, DESY5, PantheonPlus, and DESY1 data. The dashed and dash-dotted lines represent the lower bounds of neutrino mass in the NH and IH, respectively. Upper panel: A comparison of the 1D marginalized posterior distributions for $\sum m_{\nu}$ in the $\Lambda$CDM+$\sum m_\nu+N_\mathrm{eff}$, $w$CDM+$\sum m_\nu+N_\mathrm{eff}$, and $w_0w_a$CDM+$\sum m_\nu+N_\mathrm{eff}$ models using CMB+DESI+DESY5+DESY1 data. Lower panel: A comparison of the 1D marginalized posterior distributions for $\sum m_{\nu}$ in the $w_0w_a$CDM+$\sum m_\nu+N_\mathrm{eff}$ models using CMB+DESI+DESY5, CMB+DESI+DESY5+DESY1, and CMB+DESI+PantheonPlus+DESY1 data.
• Figure 2: A comparison of the two-dimensional marginalized contours between $\sum m_{\nu}$ and various other cosmological parameters using CMB+DESI+DESY5+DESY1 data.
• Figure 3: The redshift evolution of $\mathcal{E}(z)$. The gray solid curve denotes the $\Lambda$CDM model, while the blue solid curve corresponds to the $w$CDM model constrained by CMB+DESI+DESY5+DESY1 data ($w=-0.955$). The pink dashed curve represents the $w_0w_a$CDM model using CMB+DESI+PantheonPlus+DESY1 ($w_0=-0.845$, $w_a=-0.58$). The orange dash-dotted curve is the $w_0w_a$CDM constraints from CMB+DESI+DESY5+DESY1 ($w_0=-0.746$, $w_a=-0.91$).
• Figure 4: The 1D marginalized posterior distributions of $\sum m_{\nu}$ in the $w_{0}w_{a}\mathrm{CDM} + \sum m_{\nu} + N_{\rm eff}$ model. The CMB+DESI+DESY5 constraint is regarded as the baseline, shown together with the inclusion of $2\sigma$ and $5\sigma$ priors of dynamical DE.