Improvement of cosmological neutrino mass bounds

The most recent measurements of the temperature and low-multipole polarization anisotropies of the cosmic microwave background from the Planck satellite, when combined with galaxy clustering data from the Baryon Oscillation Spectroscopic Survey in the form of the full shape of the power spectrum, and with baryon acoustic oscillation measurements, provide a 95% confidence level (C.L.) upper bound on the sum of the three active neutrinos $\sum m_{\nu }<0.183\mathrm{eV}$, among the tightest neutrino mass bounds in the literature, to date, when the same data sets are taken into account. This very same data combination is able to set, at $\sim 70\%$ C.L., an upper limit on $\sum m_{\nu }$ of 0.0968 eV, a value that approximately corresponds to the minimal mass expected in the inverted neutrino mass hierarchy scenario. If high-multipole polarization data from Planck is also considered, the 95% C.L. upper bound is tightened to $\sum m_{\nu }<0.176\mathrm{eV}$. Further improvements are obtained by considering recent measurements of the Hubble parameter. These limits are obtained assuming a specific nondegenerate neutrino mass spectrum; they slightly worsen when considering other degenerate neutrino mass schemes. Low-redshift quantities, such as the Hubble constant or the reionization optical depth, play a very important role when setting the neutrino mass constraints. We also comment on the eventual shifts in the cosmological bounds on $\sum m_{\nu }$ when possible variations in the former two quantities are addressed.

Figure 1

Top: Nonlinear matter power spectrum computed using the halofit method with the camb code [28] (blue line) and the Coyote emulator (green line) of Kwan et al. (2015) [29] at $z=0.57$ for the $\mathrm{\Lambda }\mathrm{CDM}$ best-fit parameters from Planck TT 2015 data. Data points are the clustering measurements from the BOSS Data Release 9 (DR9) CMASS sample. The error bars are computed from the diagonal elements $C_{ii}$ of the covariance matrix. We also illustrate the data after applying a maximal correction for systematics, i.e., $S=1$; see text for details. Bottom: Residuals with respect to the nonlinear model with halofit. The orange horizontal line indicates the $k$ range used in our analysis.

Figure 2

One-dimensional posterior probability for $\sum m_{\nu }$ for the Base combination, which consists of Planck TT and DR9 galaxy clustering measurements, and also combined with other possible data sets. Both the one (solid lines) and the two (dashed lines) massive neutrino cases are illustrated.

Figure 3

As in Fig. 2 but focusing on the Base combination only. Different curves show the impact of marginalizing over bias, shot noise, and systematics; see text for details.