Upper Bound of 0.28 eV on Neutrino Masses from the Largest Photometric Redshift Survey

We present a new limit of $\sum _{}^{}{m}_{\nu }\le 0.28$ ($95\%$ CL) on the sum of the neutrino masses assuming a flat $\Lambda \mathrm{CDM}$ cosmology. This relaxes slightly to $\sum _{}^{}{m}_{\nu }\le 0.34$ and $\sum _{}^{}{m}_{\nu }\le 0.47$ when quasinonlinear scales are removed and $w\ne -1$, respectively. These are derived from a new photometric catalogue of over 700 000 luminous red galaxies (MegaZ DR7) with a volume of $3.3(\mathrm{Gpc}{\mathrm{h}}^{-1}{)}^3$ and redshift range $0.45<z<0.65$. The data are combined with WMAP 5-year CMB, baryon acoustic oscillations, supernovae, and a Hubble Space Telescope prior on $h$. When combined with WMAP these data are as constraining as adding all supernovae and baryon oscillation data available. The upper limit is one of the tightest constraints on the neutrino from cosmology or particle physics. Further, if these bounds hold, they all predict that current-to-next generation neutrino experiments, such as KATRIN, are unlikely to obtain a detection.

Figure 1

The best fit angular power spectra $C_l$ in the combined analysis (solid lines) are plotted over the MegaZ DR7 data. The panels relate to four redshift bins with width $\Delta z=0.05$ from $z=0.45$ (main panel) to $z=0.65$ (panel 4). These spectra are good fits to the galaxy statistics including scales not utilized in the analysis ($l>300$). The fit is also plotted for linear spectra (dashed lines) and highlights the scale at which the nonlinear regime starts to become significant. The dotted line demonstrates the effect of introducing $\sum _{}^{}{m}_{\nu }=1\mathrm{eV}$ neutrinos with all parameters, except ${\Omega }_c$, held fixed.

Figure 2

Left Panel: The marginalized 1D distribution for the neutrino from three incrementally combined analyses. The vertical dashed lines correspond to 95% confidence levels. Other Panels: 68% and 95% marginalized distributions for the matter density ${\Omega }_m$, Hubble parameter $h$, and spectral index $n_s$ against the total neutrino masses. The contours correspond to (from bottom layer) WMAP-only (red/dark), $\mathrm{WMAP}+\mathrm{\text{Mega}}\mathrm{Z}$ (yellow/light), $\mathrm{WMAP}+\mathrm{SNe}+\mathrm{BAO}$ (blue/dark), and $\mathrm{WMAP}+\mathrm{SNe}+\mathrm{BAO}+\mathrm{\text{Mega}}\mathrm{Z}+\mathrm{HST}$ (green/light). Table  highlights that the vast majority of the gain in the last two contours originates from the new and complementary galaxy clustering data.

Figure 3

The 2D 68% and 95% contours and marginalized 1D distributions for 7 cosmological parameters (${\Omega }_b{h}^2$, ${\Omega }_c{h}^2$, ${\Omega }_{\Lambda }$, $n_s$, $\tau$, $\ln ({10}^{10}{A}_s)$, and $\sum _{}^{}{m}_{\nu }$) in a $\mathrm{WMAP}5+\mathrm{SNe}+\mathrm{BAO}+\mathrm{\text{Mega}}\mathrm{Z}$ $\mathrm{DR}7+\mathrm{HST}$ combined constraint (red contours). The amplitude of the Sunyaev-Zeldovich fluctuations ($A_{\mathrm{SZ}}$) and four bias parameters ($b_1$, $b_2$, $b_3$, $b_4$) are marginalized over but not plotted. The black contours are given for the WMAP-only analysis.