More accurate simulations with separate initial conditions for baryons and dark matter

Abstract

We revisit techniques for performing cosmological simulations with both baryons and cold dark matter when each fluid has different initial conditions, as is the case at the end of the radiation era. Most simulations do not reproduce the linear prediction for the difference between the cold dark matter and baryon perturbations. We show that this is due to the common use of offset regular grids when setting up the particle initial conditions. The correct behaviour can be obtained without any loss of simulation resolution by using a Lagrangian glass for the baryon particles. We further show that the difference between cold dark matter and baryons may affect predictions for the Lyman-alpha forest flux power spectrum at the 5% level, potentially impacting current cosmological constraints.

18 pages, 6 figures. Accepted to JCAP

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• A hydrodynamical halo model for weak-lensing cross correlations
• Higher-order initial conditions for mixed baryon-CDM simulations
• Simulating intergalactic gas for DESI-like small scale Lymanα forest observations
• Cosmological perturbations for two cold fluids in $\Lambda$CDM
• PRIYA: A New Suite of Lyman-alpha Forest Simulations for Cosmology
• Cosmological Constraints from the eBOSS Lyman-$\alpha$ Forest using the PRIYA Simulations
• The effect of inhomogeneous reionisation on the Lyman-$\alpha$ forest power spectrum at redshift $z>4$: implications for thermal parameter recovery
• Neutrino mass bounds from confronting an effective model with BOSS Lyman-alpha data
• The BAHAMAS project: Effects of dynamical dark energy on large-scale structure
• First Structure Formation under the Influence of Gas-Dark Matter Streaming Velocity and Density: Impact of the Baryons-trace-dark matter Approximation
• Simulating Hydrodynamics in Cosmology with CRK-HACC
• A Multi-Fidelity Emulator for the Lyman-$\alpha$ Forest Flux Power Spectrum
• Improving initialization and evolution accuracy of cosmological neutrino simulations
• Particle initialization effects on Lyman-$\alpha$ forest statistics in cosmological SPH simulations
• Numerical Discreteness Errors in Multi-Species Cosmological N-body Simulations
• Effect of Separate Initial Conditions on the Lyman-$\alpha$ Forest in Simulations
• ForestFlow: predicting the Lyman-$\alpha$ forest clustering from linear to nonlinear scales
• Baryonic effects in the Effective Field Theory of Large-Scale Structure and an analytic recipe for lensing in CMB-S4
• Effects of dynamical friction on perturbations for evolving dark energy
• Particle loads for cosmological simulations with equal-mass dark matter and baryonic particles
• Cosmic voids and BAO with relative baryon-CDM perturbations