Suite of hydrodynamical simulations for the Lyman-α forest with massive neutrinos
Abstract
The signature left in quasar spectra by neutral hydrogen in the Universe allows
constraining the sum of the neutrino masses with a better sensitivity than laboratory
experiments and may shed new light on the neutrino mass hierarchy and 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-α (Lyα) forest on scales ranging from a few to hundreds
of megaparsecs, which in turn 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 (CDM), baryons and massive neutrinos, specifically
targeted for modeling the low-density regions of the intergalactic medium (IGM) as probed
by the Lyα
forest at high-redshift. The simulations span volumes ranging from (25 h-1
Mpc)3 to (100
h-1 Mpc)3, and were made using
either 3 × 1923 ≃
21 million or 3 ×
7683 ≃ 1.4 billion particles. The resolution of the
various runs was further enhanced, so that we reached the equivalent of 3 × 30723 ≃ 87 billion particles
in a (100 h-1
Mpc)3 box size. The chosen cosmological parameters are
compatible with the latest Planck 2013 results, although we also explored
the effect of slight variations in the main cosmological and astrophysical parameters. We
adopted a particle-type implementation of massive neutrinos, and consider three degenerate
species with masses ∑
mν =
0.1,0.2,0.3,0.4,
and 0.8 eV, respectively. We
improved on previous studies in several ways, in particular with updated routines for IGM
radiative cooling and heating processes, and initial conditions based on second-order
Lagrangian perturbation theory (2LPT) rather than the Zel’dovich approximation. This
allowed us to safely start our runs at relatively low redshift (z = 30), which reduced the
shot-noise contamination in the neutrino component and the CPU consumption. In addition to
providing technical details on the simulations, we present the first analysis of the
nonlinear three- and one-dimensional matter and flux power spectra from these models, and
characterize the statistics of the transmitted flux in the Lyα forest including the
effect of massive neutrinos. In synergy with recent data from the Baryon Acoustic
Spectroscopic Survey (BOSS) and the Planck satellite, and with a grid of
corresponding neutrino-less simulations, our realizations will allow us to constrain
cosmological parameters and neutrino masses directly from the Lyα forest with improved
sensitivity. In addition, our simulations can be useful for a broader variety of
cosmological and astrophysical applications, ranging from the three-dimensional modeling
of the Lyα
forest to cross-correlations between different probes, studying the expansion history of
the Universe including massive neutrinos, and particle-physics related topics. Moreover,
while our simulations have been specifically designed to meet the requirements of the BOSS
survey, they can also be used for upcoming or future experiments – such as eBOSS and
DESI.
Origin : Publication funded by an institution
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