Constraint on neutrino masses from SDSS-III/BOSS Ly$α$ forest and other cosmological probes

TL;DR

The paper addresses constraining the total neutrino mass $\sum m_\nu$ using Lyα forest data from BOSS in combination with Planck CMB measurements and BAO within a ΛCDM framework. It employs hydrodynamical simulations that include massive neutrinos and a second-order Taylor expansion of the simulated power spectrum to interpret the Lyα 1D flux power spectrum. The Lyα data alone yield an upper bound of $\sum m_\nu < 1.1\,\mathrm{eV}$ (95% CL), while combining Lyα with Planck CMB tightens this to $\sum m_\nu < 0.15\,\mathrm{eV}$ (95% CL), with BAO further reducing it to $\sum m_\nu < 0.14\,\mathrm{eV}$ (95% CL). The bound is robust to statistical approach and data combinations, and given the measured $\Delta m^2$ values, the results tend to favor the normal hierarchy for the active neutrino masses.

Abstract

We present constraints on the parameters of the $Λ$CDM cosmological model in the presence of massive neutrinos, using the one-dimensional Ly$α$ forest power spectrum obtained with the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS) by Palanque-Delabrouille et al. (2013), complemented by additional cosmological probes. The interpretation of the measured Ly$α$ spectrum is done using a second-order Taylor expansion of the simulated power spectrum. BOSS Ly$α$ data alone provide better bounds than previous Ly$α$ results, but are still poorly constraining, especially for the sum of neutrino masses $\sum m_ν$, for which we obtain an upper bound of 1.1~eV (95\% CL), including systematics for both data and simulations. Ly$α$ constraints on $Λ$CDM parameters and neutrino masses are compatible with CMB bounds from the Planck collaboration. Interestingly, the combination of Ly$α$ 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, $\sum m_ν< 0.15$~eV at 95\% CL (with a best-fit in zero). Adding recent BAO results further tightens this constraint to $\sum m_ν< 0.14$~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$α$. Given the measured values of the two squared mass differences $Δm^2$, this result tends to favor the normal hierarchy scenario against the inverted hierarchy scenario for the masses of the active neutrino species.

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