Possible evidence for a large-scale enhancement in the Lyman-$\alpha$ forest power spectrum at redshift $\text{z}\ge 4$

Abstract

Inhomogeneous reionization enhances the 1D Lyman-$\alpha$ forest power spectrum on large scales at redshifts $z\ge 4$. This is due to coherent fluctuations in the ionized hydrogen fraction that arise from large-scale variations in the post-reionization gas temperature, which fade as the gas cools. It is therefore possible to use these relic fluctuations to constrain inhomogeneous reionization with the power spectrum at wavenumbers ${\log }_{10}(k/\mathrm{k}{\mathrm{m}}^{-1}\mathrm{s})\lesssim -1.5$. We use the Sherwood-Relics suite of hybrid radiation hydrodynamical simulations to perform a first analysis of new Lyman-$\alpha$ forest power spectrum measurements at $4.0\le z\le 4.6$. These data extend to wavenumbers ${\log }_{10}(k/\mathrm{k}{\mathrm{m}}^{-1}\mathrm{s})\simeq -3$, with a relative uncertainty of $10$--$20$ per cent in each wavenumber bin. Our analysis returns a $2.7\sigma$ preference for an enhancement in the Lyman-$\alpha$ forest power spectrum at large scales, in excess of that expected for a spatially uniform ultraviolet background. This large-scale enhancement could be a signature of inhomogeneous reionization, although the statistical precision of these data is not yet sufficient for obtaining a robust detection of the relic post-reionization fluctuations. We show that future power spectrum measurements with relative uncertainties of $\lesssim 2.5$ per cent should provide unambiguous evidence for an enhancement in the power spectrum on large scales.

Accepted by MNRAS, 13 pages, 8 figures

References in corpus (20)

• Observational constraints on Cosmic Reionization
• Model-independent evidence in favor of an end to reionization by z~6
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Can sterile neutrinos be the dark matter?
• Hydrogen reionisation ends by $z=5.3$: Lyman-$\alpha$ optical depth measured by the XQR-30 sample
• XQ-100: A legacy survey of one hundred 3.5 < z < 4.5 quasars observed with VLT/XSHOOTER
• The thermal history of the intergalactic medium down to redshift z=1.5: a new curvature measurement
• The PHLEK Survey: A New Determination of the Primordial Helium Abundance
• The Lyman-alpha forest power spectrum from the XQ-100 Legacy Survey
• The Second Data Release of the KODIAQ Survey
• The Sherwood-Relics simulations: overview and impact of patchy reionization and pressure smoothing on the intergalactic medium
• A New Precision Measurement of the Small-Scale Line-of-Sight Power Spectrum of the Ly$\alpha$ Forest
• An emulator for the Lyman-$\alpha$ forest in beyond-$\Lambda$CDM cosmologies
• Optimal 1D Ly$\alpha$ Forest Power Spectrum Estimation -- II. KODIAQ, SQUAD & XQ-100
• Simulating the effect of high column density absorbers on the one-dimensional Lyman-alpha forest flux power spectrum
• Probing the Epoch of Reionization with the Lyman Alpha Forest at z~4-5
• Optimal 1D Ly-$\alpha$ Forest Power Spectrum Estimation I: DESI-Lite Spectra
• The Effect Of AGN Heating On The Low-Redshift Lyα Forest
• The effect of inhomogeneous reionisation on the Lyman-$\alpha$ forest power spectrum at redshift $z>4$: implications for thermal parameter recovery
• A Multi-Fidelity Emulator for the Lyman-$\alpha$ Forest Flux Power Spectrum

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• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Unveiling Dark Matter free-streaming at the smallest scales with high redshift Lyman-alpha forest
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• Constraining Mixed Dark Matter models with high redshift Lyman-alpha forest data
• The Lyman-limit photon mean free path at the end of late reionisation in the Sherwood-Relics simulations
• The long-lasting effect of X-ray preheating in the post-reionization intergalactic medium
• ForestFlow: predicting the Lyman-$\alpha$ forest clustering from linear to nonlinear scales
• Parameter estimation from Ly$\alpha$ forest in Fourier space using Information Maximising Neural Network
• Neural network emulator to constrain the high-$z$ IGM thermal state from Lyman-$\alpha$ forest flux auto-correlation function