Cosmological Constraints from the eBOSS Lyman-$\alpha$ Forest using the PRIYA Simulations

Abstract

We present new cosmological parameter constraints from the eBOSS Lyman-$\alpha$ forest survey. We use a new theoretical model and likelihood based on the PRIYA simulation suite. PRIYA is the first suite to resolve the Lyman-$\alpha$ forest in a ($120$~Mpc/h~)${}^3$ volume, using a multi-fidelity emulation technique. We use PRIYA to predict Lyman-$\alpha$ forest observables with $\lesssim 1\%$ interpolation error over an $11$ dimensional ($9$ simulated, $2$ in post-processing) parameter space. We identify an internal tension within the flux power spectrum data. Once the discrepant data is removed, we find the primeval scalar spectral index measured at a pivot scale of $k_0=0.78$ Mpc${}^{-1}$ to be $n_P=1.009_{-0.018}^{+0.027}$ at 68\% confidence. This measurement from the Lyman-$\alpha$ forest flux power spectrum alone is in reasonable agreement with Planck, and in tension with earlier eBOSS analyses. The amplitude of matter fluctuations is ${\sigma }_8=0.733_{-0.029}^{+0.026}$ at 68\% confidence, in agreement with Dark Energy Survey weak lensing measurements and other small-scale structure probes and in tension with CMB measurements from Planck and ACT. The effective optical depth to Lyman-$\alpha$ photons from our pipeline is in good agreement with earlier high resolution measurements. We find a linear power at $z=3$ and $k=0.009$ s/km of ${\Delta }_L^2=0.302_{-0.027}^{+0.024}$ with a slope $n_{\mathrm{eff}}=-2.264_{-0.018}^{+0.026}$. Our flux power spectrum only chains prefer a low level of heating during helium reionization. When we add IGM temperature data we find $n_P=0.983\pm 0.020$ and ${\sigma }_8=0.703_{-0.027}^{+0.023}$. Our chains prefer an early and long helium reionization event, as suggested by measurements from the helium Lyman-$\alpha$ forest. In the near future we will use our pipeline to infer cosmological parameters from the DESI Lyman-$\alpha$ data.

41 pages, 13 figures, published in JCAP https://iopscience.iop.org/article/10.1088/1475-7516/2024/07/029

References in corpus (22)

• The DESI Experiment Part I: Science,Targeting, and Survey Design
• Cosmological parameters from combining the Lyman-alpha forest with CMB, galaxy clustering and SN constraints
• The Cosmic Linear Anisotropy Solving System (CLASS) I: Overview
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Baryon acoustic oscillations with Lyman-$\alpha$ forests
• Possible evidence for an inverted temperature-density relation in the intergalactic medium from the flux distribution of the Lyman-alpha forest
• An improved measurement of the flux distribution of the Ly-alpha forest in QSO absorption spectra: the effect of continuum fitting, metal contamination and noise properties
• Minimally Parametric Power Spectrum Reconstruction from the Lyman-alpha Forest
• The Mira-Titan Universe II: Matter Power Spectrum Emulation
• Constraint on neutrino masses from SDSS-III/BOSS Ly$\alpha$ forest and other cosmological probes
• The End of Helium Reionization at z~2.7 Inferred from Cosmic Variance in HST/COS HeII Lyman Alpha Absorption Spectra
• The Lyman-alpha forest power spectrum from the XQ-100 Legacy Survey
• Reproducing the Kinematics of Damped Lyman-alpha Systems
• The Lyman-alpha forest and WMAP year three
• The Second Data Release of the KODIAQ Survey
• Emulation of physical processes with Emukit
• The Dark Energy Spectroscopic Instrument: One-dimensional power spectrum from first Lyman-$\alpha$ forest samples with Fast Fourier Transform
• Simulating the effect of high column density absorbers on the one-dimensional Lyman-alpha forest flux power spectrum
• The Implications of Gunn-Peterson Troughs in the HeII Lyman-alpha Forest
• Simulating intergalactic gas for DESI-like small scale Lymanα forest observations
• PRIYA: A New Suite of Lyman-alpha Forest Simulations for Cosmology
• Impact of inhomogeneous reionization on the Lyman-α forest
• A Multi-Fidelity Emulator for the Lyman-$\alpha$ Forest Flux Power Spectrum

Cited by in corpus (6)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• $5\sigma$ tension between Planck cosmic microwave background and eBOSS Lyman-alpha forest and constraints on physics beyond $\Lambda$CDM
• Fresh Look at Neutrino Self-Interactions With the Lyman-$\alpha$ Forest: Constraints from EFT and PRIYA Simulations
• Hunting Primordial Black Hole Dark Matter in Lyman-$\alpha$ Forest
• Signatures of Very Early Dark Energy in the Matter Power Spectrum
• Updated constraints on the primordial power spectrum at sub-Mpc scales