Constraints on neutrino masses from Lyman-alpha forest power spectrum with BOSS and XQ-100

Abstract

We present constraints on masses of active and sterile neutrinos in the context of the ΛCDMν and ΛWDM models, respectively. We use the one-dimensional Lyα-forest power spectrum from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) measured by Palanque-Delabrouille et al. [1], and from the VLT/XSHOOTER legacy survey (XQ-100). In this paper, we present our own measurement of the publicly released XQ-100 quasar spectra, focusing in particular on an improved determination of the spectrograph resolution that allows us to push to smaller scales than the public release and reach k-modes of 0.070 s km^-1. We compare the obtained 1D Lyα flux power spectrum to the one measured by Irsic et al. [2] to k-modes of 0.057 s km^-1. Fitting Lyα data alone leads to cosmological parameters in excellent agreement with the values derived independently from Planck 2015 Cosmic Microwave Background (CMB) data. Combining BOSS and XQ-100 Lyα power spectra, we constrain the sum of neutrino masses to ∑ m_ν < 0.8 eV (95% C.L.) including all identified sources of systematic uncertainties. With the addition of CMB data, this bound is tightened to ∑ m_ν < 0.14 eV (95% C.L.). With their sensitivity to small scales, Lyα data are ideal to constrain ΛWDM models. Using XQ-100 alone, we issue lower bounds on pure dark matter particles: m_X gtrsim 2.08 : keV (95% C.L.) for early decoupled thermal relics, and m_s gtrsim 10.2 : keV (95% C.L.) for non-resonantly produced right-handed neutrinos. Combining the 1D Lyα-forest power spectrum measured by BOSS and XQ-100, we improve the two bounds to m_X gtrsim 4.17 : keV and m_s gtrsim 25.0 : keV (95% C.L.), slightly more constraining than what was achieved in Baur et al. 2015 [3] with BOSS data alone. The 3 σ bound shows a more significant improvement, increasing from m_X gtrsim 2.74 : keV for BOSS alone to m_X gtrsim 3.10 : keV for the combined BOSS+XQ-100 data set. Finally, we include in our analysis the first two redshift bins (z = 4.2 and z = 4.6) of the power spectrum measured by Viel et al. 2013 [4] with the high-resolution HIRES/MIKE spectrographs. The addition of HIRES/MIKE power spectrum allows us to further improve the two limits to m_X gtrsim 4.65 : keV and m_s gtrsim 28.8 : keV (95% C.L.).