We present constraints on the parameters of the \Lambda CDM cosmological model in the presence of massive neutrinos , using the one-dimensional Ly \alpha forest power spectrum obtained with the Baryon Oscillation Spectroscopic Survey ( BOSS ) of the Sloan Digital Sky Survey ( SDSS ) by , complemented by additional cosmological probes .
The interpretation of the measured Ly \alpha spectrum is done using a second-order Taylor expansion of the simulated power spectrum .
BOSS Ly \alpha data alone provide better bounds than previous Ly \alpha results , but are still poorly constraining , especially for the sum of neutrino masses \sum m _ { \nu } , for which we obtain an upper bound of 1.1 eV ( 95 % CL ) , including systematics for both data and simulations .
Ly \alpha constraints on \Lambda CDM parameters and neutrino masses are compatible with CMB bounds from the Planck collaboration [ ] .
Interestingly , the combination of Ly \alpha with CMB data reduces the uncertainties significantly , due to very different directions of degeneracy in parameter space , leading to the strongest cosmological bound to date on the total neutrino mass , \sum m _ { \nu } < 0.15 eV at 95 % CL ( with a best-fit in zero ) .
Adding recent BAO results further tightens this constraint to \sum m _ { \nu } < 0.14 eV at 95 % CL .
This bound is nearly independent of the statistical approach used , and of the different combinations of CMB and BAO data sets considered in this paper in addition to Ly \alpha .
Given the measured values of the two squared mass differences \Delta m ^ { 2 } , this result tends to favor the normal hierarchy scenario against the inverted hierarchy scenario for the masses of the active neutrino species .