Emulating the Lyman-Alpha forest 1D power spectrum from cosmological simulations: New models and constraints from the eBOSS measurement

2024/12/06 by Walther, Michael, Schöneberg, Nils, Chabanier, Solène +8 · 5 citations
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences

paper · doi:10.48550/arxiv.2412.05372

Abstract

We present the Lyssa suite of high-resolution cosmological simulations of the Lyman-α forest designed for cosmological analyses. These 18 simulations have been run using the Nyx code with 4096³ hydrodynamical cells in a 120 Mpc (∼ 81Mpc/h) comoving box and individually provide sub-percent level convergence of the Lyman-α forest 1d flux power spectrum. We build a Gaussian process emulator for the Lyssa simulations in the lym1d likelihood framework to interpolate the power spectrum at arbitrary parameter values. We validate this emulator based on leave-one-out tests and based on the parameter constraints for simulations outside of the training set. We also perform comparisons with a previous emulator, showing a percent level accuracy and a good recovery of the expected cosmological parameters. Using this emulator we derive constraints on the linear matter power spectrum amplitude and slope parameters A_Lyα and n_Lyα. While the best-fit Planck ΛCDM model has A_Lyα=8.79 and n_Lyα=-2.363, from DR14 eBOSS data we find that A_Lyα<7.6 (95% CI) and n_Lyα=-2.369 ± 0.008. The low value of A_Lyα, in tension with Planck, is driven by the correlation of this parameter with the mean transmission of the Lyman-α forest. This tension disappears when imposing a well-motivated external prior on this mean transmission, in which case we find A_Lyα=9.8±1.1 in accordance with Planck.

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• Nyx-RT: Adaptive Ray Tracing in the Nyx Hydrodynamical Code
• Bayesian inference on Calabi--Yau moduli spaces and the axiverse: experimental data meets string theory
• Small-scale Lyman alpha forest cosmology with PRIYA: Constraints from XQ100 and KODIAQ-SQUAD one-dimensional flux power spectra
• Generation of Lognormal Synthetic Lyman-α Forest Spectra for P_1D Analysis
• Cosmological neutrino mass: a frequentist overview in light of DESI

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