Possible evidences for cosmological massive neutrinos

Abstract

A key question in cosmology is whether massive neutrinos exist on cosmic scales. Current cosmological observations have severely compressed the viable range for neutrino masses and even prefer phenomenologically an effective negative mass. This poses a great challenge to the cosmological search for neutrinos. Based on current background and large scale structure data, taking a full red-shift and/or scale tomography method, we obtain one beyond \(5\,\sigma\), two \(3\,\sigma\), and two \(2\,\sigma\) evidences of massive neutrinos, spanning both high and low red-shifts, as well as both small and intermediate scales. Specifically, for the case of red-shift tomography, we find the neutrino mass sum \(\Sigma m_\nu ^{1}=1.01^{+0.47}_{-0.58}\) eV in \(z \in [0, 1]\) using the data combination of CMB, BAO, and supernova, indicating a \(2\,\sigma\) clue of nonzero neutrino mass, while the addition of WiggleZ galaxy power spectrum leads to \(\Sigma m_\nu ^{1}=0.65\pm 0.25\) eV, implying a \(3\,\sigma\) evidence of massive neutrinos. For the case of scale tomography, we give \(\Sigma m_\nu ^{k1}=0.75^{+0.20}_{-0.27}\) eV in \(k \in [10^{-1}, +\infty )\) h Mpc\(^{-1}\) using the combination of CMB and WiggleZ observations, revealing a beyond \(5\,\sigma\) evidence of massive neutrinos at small scales, while combining CMB with DESY1 galaxy clustering, cosmic shear and galaxy–galaxy lensing data provides \(\Sigma m_\nu ^{k2}=0.55\pm 0.27\) eV in \(k \in [10^{-2}, 10^{-1}]\) h Mpc\(^{-1}\), giving a \(2\,\sigma\) hint at intermediate scales. For the case of red-shift and scale tomography, we obtain \(\Sigma m_\nu ^{52}=0.63^{+0.20}_{-0.24}\) eV when \(z \in [100, 1100]\) and \(k \in [10^{-2}, 10^{-1}]\) h Mpc\(^{-1}\), suggesting a \(\sim 3\,\sigma\) evidence of massive neutrinos. Interestingly, these five signals of nonzero neutrino masses are well consistent within \(1\,\sigma\) confidence level, indicating a possible suppression of neutrino mass during the evolution of the universe. Using cosmic microwave background observations to constrain a red-shift and scale dependent neutrino mass, we make the first neutrino mass map through the cosmic history and full scales for future high-precision search. Our results could help understand the role massive neutrinos played in the evolution of the universe.