Papers › Direct cosmological inference from three-dimensional correlations of the Lyman-α forest

Direct cosmological inference from three-dimensional correlations of the Lyman-α forest

22 Sep 2022arXiv:2209.11263links table onlyarchive 2025-07-28

Francesca Gerardi, Andrei Cuceu, Andreu Font-Ribera, Benjamin Joachimi, Pablo Lemos

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When performing cosmological inference, standard analyses of the Lyman-α (Lyα) 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 Lyα auto-correlation functions and cross-correlations with quasars at effective redshift z_(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 Ω_M, which is about three to four times better than what BAO alone can probe. The growth term f σ₈ (z_(eff)) is constrained to the 10% level, and the spectral index nₛ to ∼3-4%. We demonstrate that the extra information resulting from our `direct fit' approach, except for the nₛ constraint, can be traced back to the Alcock-Paczy\'nski effect and redshift space distortion information.

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