Direct cosmological inference from three-dimensional correlations of the Lyman-$\alpha$ forest

Abstract

When performing cosmological inference, standard analyses of the Lyman-$\alpha$ (Ly$\alpha$) three-dimensional correlation functions only consider the information carried by the distinct peak produced by baryon acoustic oscillations (BAO). In this work, we address whether this compression is sufficient to capture all the relevant cosmological information carried by these functions. We do this by performing a direct fit to the full shape, including all physical scales without compression, of synthetic Ly$\alpha$ auto-correlation functions and cross-correlations with quasars at effective redshift $z_{\mathrm{eff}}=2.3$, assuming a DESI-like survey, and providing a comparison to the classic method applied to the same dataset. Our approach leads to a $3.5\%$ constraint on the matter density ${\Omega }_{\mathrm{M}}$, which is about three to four times better than what BAO alone can probe. The growth term $f{\sigma }_8(z_{\mathrm{eff}})$ is constrained to the $10\%$ level, and the spectral index $n_{\mathrm{s}}$ to $\sim 3-4\%$. We demonstrate that the extra information resulting from our `direct fit' approach, except for the $n_{\mathrm{s}}$ constraint, can be traced back to the Alcock-Paczyński effect and redshift space distortion information.

Matches version published in MNRAS

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• The DESI Experiment Part I: Science,Targeting, and Survey Design
• Baryon Acoustic Oscillations in the Ly-α forest of BOSS quasars
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Baryon acoustic oscillations with Lyman-$\alpha$ forests
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Cited by in corpus (10)

• DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
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• Constraints on the cosmic expansion rate at redshift 2.3 from the Lyman-$\alpha$ forest
• Quasar Factor Analysis -- An Unsupervised and Probabilistic Quasar Continuum Prediction Algorithm with Latent Factor Analysis
• The Alcock-Paczyński effect from Lyman-$\alpha$ forest correlations: Analysis validation with synthetic data
• The ACCEL2 Project: Precision Measurements of EFT Parameters and BAO Peak Shifts for the Lyman-$\alpha$ Forest
• Measurement of the small-scale 3D Lyman-$\alpha$ forest power spectrum
• Hunting Primordial Black Hole Dark Matter in Lyman-$\alpha$ Forest
• ForestFlow: predicting the Lyman-$\alpha$ forest clustering from linear to nonlinear scales
• Optimal data compression for Lyman-$\alpha$ forest cosmology