Mapping Lyman-alpha forest three-dimensional large scale structure in real and redshift space

Abstract

This work presents a new physically-motivated supervised machine learning method, Hydro-BAM, to reproduce the three-dimensional Lyman-$\alpha$ forest field in real and in redshift space learning from a reference hydrodynamic simulation, thereby saving about 7 orders of magnitude in computing time. We show that our method is accurate up to $k\sim 1h{\mathrm{Mpc}}^{-1}$ in the one- (PDF), two- (power-spectra) and three-point (bi-spectra) statistics of the reconstructed fields. When compared to the reference simulation including redshift space distortions, our method achieves deviations of $\lesssim 2\%$ up to $k=0.6h{\mathrm{Mpc}}^{-1}$ in the monopole, $\lesssim 5\%$ up to $k=0.9h{\mathrm{Mpc}}^{-1}$ in the quadrupole. The bi-spectrum is well reproduced for triangle configurations with sides up to $k=0.8h{\mathrm{Mpc}}^{-1}$. In contrast, the commonly-adopted Fluctuating Gunn-Peterson approximation shows significant deviations already neglecting peculiar motions at configurations with sides of $k=0.2-0.4h{\mathrm{Mpc}}^{-1}$ in the bi-spectrum, being also significantly less accurate in the power-spectrum (within 5$\%$ up to $k=0.7h{\mathrm{Mpc}}^{-1}$). We conclude that an accurate analysis of the Lyman-$\alpha$ forest requires considering the complex baryonic thermodynamical large-scale structure relations. Our hierarchical domain specific machine learning method can efficiently exploit this and is ready to generate accurate Lyman-$\alpha$ forest mock catalogues covering large volumes required by surveys such as DESI and WEAVE.

Accepted for publication by ApJ

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• Planting a Lyman alpha forest on AbacusSummit
• LyMAS reloaded: improving the predictions of the large-scale Lyman-α forest statistics from dark matter density and velocity fields
• Tracing the high-z cosmic web with Quaia: catalogues of voids and clusters in the quasar distribution
• Modeling the Cosmological Lyman-$\alpha$ Forest at the Field Level
• Bridging Simulations and EFT: A Hybrid Model of the Lyman-Alpha Forest Field
• Differentiable Fuzzy Cosmic-Web for Field Level Inference