Abstract
The signature left in quasar spectra by the presence of neutral hydrogen in the Universe allows one to constrain the sum of the neutrino masses with improved sensitivity, with respect to laboratory experiments, and may shed a new light on the neutrino mass hierarchy and on the absolute mass scale of neutrinos. Constraints on cosmological parameters and on the dark energy equation of state can also be derived, from a joint parameter estimation procedure. However, this requires a detailed modeling of the line-of-sight power spectrum of the transmitted flux in the Lyman-Alpha (LyA) forest on scales ranging from a few to hundreds of Mpcs, which in turns demands the inclusion and careful treatment of cosmological neutrinos. To this end, we present here a suite of state-of-the-art hydrodynamical simulations with cold dark matter, baryons and massive neutrinos, specifically targeted for modeling the low-density regions of the IGM as probed by the LyA forest at high-redshift. The simulations span volumes ranging from (25 Mpc/h)^3 to (100 Mpc/h)^3, and are made using either 3 X 192^3~21 millions or 3 X 768^3~1.4 billion particles. The resolution of the various runs can be further enhanced, so that we can reach the equivalent of 3 X 3072^3~87 billion particles in a (100 Mpc/h)^3 box size. The chosen cosmological parameters are compatible with the latest Planck (2013) results, although we also explore the effect of slight variations in the main cosmological and astrophysical parameters. We adopt a particle-type implementation of massive neutrinos, and consider three degenerate species having masses M_nu =0.1, 0.2, 0.3, 0.4 and 0.8 eV, respectively. We improve on previous studies in several ways, in particular with updated routines for IGM radiative cooling and heating processes, and initial conditions based on 2LPT rather than the Zeldovich approximation.
Highlights
Neutrino science has received a boost of attention recently because the breakthrough discovery in particle physics over the last decade that neutrinos are massive
The overall physical picture that emerges is relatively simple: the intergalactic medium (IGM) probed by the Lyα forest consists of mildly nonlinear gas density fluctuations; low column-density absorption lines trace the filaments of the cosmic web; high column-density absorption lines trace the surrondings of galaxies; the gas traces the dark matter, and is photoionized and photoheated by the UV-background
Viel et al (2010) previously compared particle and grid neutrino representations and found that their difference in terms of power spectra are mainly driven by the fact that the nonlinear evolution at small scales is not properly reproduced by the grid method; they argued that on scales relevant for the Lyα forest it provides higher accuracy to account for the nonlinear evolution rather than limiting the description to the linear case, despite the effect of the Poisson contribution on the neutrino power spectrum introduced by the particle-based modeling
Summary
Neutrino science has received a boost of attention recently because the breakthrough discovery in particle physics over the last decade that neutrinos are massive. The Lyα forest is well suited to constrain neutrino masses, since massive neutrinos leave a redshift- and mass-dependent signature in the one-dimensional flux power spectrum because the growth of cosmological structures on scales smaller than the neutrino free-streaming distance is suppressed To detect this effect, careful modeling of the line-ofsight (LOS) power spectrum of the transmitted Lyα flux is required. In addition to providing technical details on the simulations and on the improvements made with respect to pre-existing literature, we show here measurements of the simulated nonlinear three- and one-dimensional matter and flux power spectra, and characterize the statistics of the transmitted flux in the Lyα forest in presence of massive neutrinos This is the first of a series of papers dedicated to quantify the effects of massive neutrinos in the Lyα forest across different redshift slices and at nonlinear scales.
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