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

TL;DR

If these bounds hold, they all predict that current-to-next generation neutrino experiments, such as KATRIN, are unlikely to obtain a detection.

Abstract

We present a new upper limit of sum m_ν eV < 0.28 (95% CL) on the sum of the neutrino masses assuming a flat LCDM cosmology. This relaxes slightly to sum m_ν < 0.34 and sum m_ν < 0.47 when quasi non-linear scales are removed and w is not equal to -1, respectively. These bounds are derived from a new photometric redshift catalogue of over 700,000 Luminous Red Galaxies (MegaZ DR7) with a volume of 3.3 (Gpc h^-1)^3, extending over the redshift range 0.45 < z < 0.65 and up to angular scales of l_max = 300. The data are combined with WMAP 5-year CMB fluctuations, Baryon Acoustic Oscillations (BAO), type 1a Supernovae (SNe) and an HST prior on the Hubble parameter. This is the first combined constraint from a photometric redshift catalogue with other cosmological probes. When combined with WMAP this data set proves to be as constraining as the addition of all SNe and BAO data available to date. The upper limit is one of the tightest and `cleanest' constraints on the neutrino mass from cosmology or particle physics. Furthermore, if the aforementioned bounds hold, they all predict that current-to-next generation neutrino experiments, such as KATRIN, are unlikely to obtain a detection.

Figures (3)

• Figure 1: The best fit angular power spectra $C_{\ell}$ 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 utilised in the analysis ($\ell > 300$). The fit is also plotted for linear spectra (dashed lines) and highlights the scale at which the non-linear regime starts to become significant. The dotted line demonstrates the effect of introducing $\sum m_{\nu} = 1$ eV neutrinos with all parameters, except $\Omega_{c}$, held fixed.
• Figure 2: Left Panel: The marginalised 1D distribution for the neutrino from three incrementally combined analyses. The vertical dashed lines correspond to $95\%$ confidence levels. Other Panels:$68\%$ and $95\%$ marginalised 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), WMAP+MegaZ (yellow/light), WMAP+SNe+BAO (blue/dark) and WMAP+SNe+BAO+MegaZ+HST (green/light). Table \ref{['table:neutrinosummary']} 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 marginalised 1D distributions for 7 cosmological parameters ($\Omega_{b} h^{2}$, $\Omega_{c} h^{2}$, $\Omega_{\Lambda}$, $n_{s}$, $\tau$, $\mathrm{ln} (10^{10} A_{s})$ and $\sum m_{\nu}$) in a WMAP5 + SNe + BAO + MegaZ DR7 + HST combined constraint (red contours). The amplitude of the Sunyaev-Zeldovich fluctuations ($A_{SZ}$) and four bias parameters ($b_{1}$, $b_{2}$, $b_{3}$, $b_{4}$) are marginalised over but not plotted. The black contours are given for the WMAP-only analysis.