Modeling the Cosmological Lyman-α Forest at the Field Level

Area of Science:

• Cosmology
• Astrophysics
• Intergalactic Medium

Background:

• The Lyman-alpha (Ly-α) forest, a series of absorption lines in quasar spectra, is vital for probing the intergalactic medium and cosmology at high redshifts.
• Current redshift surveys require precise theoretical tools to accurately model the Ly-α forest's complex distribution.

Purpose of the Study:

• To develop an analytic, perturbative forward model for predicting the Ly-α forest at the field level.
• To provide precise theoretical tools for analyzing large-scale structure and cosmological parameters from Ly-α forest data.

Main Methods:

• Developed an analytic, perturbative forward model to predict Ly-α forest flux.
• Compared model predictions against the Sherwood hydrodynamic simulations.
• Evaluated the model's performance on the Ly-α forest flux power spectrum, its cross-correlation with dark matter halos, and the one-point probability distribution function.

Main Results:

• The analytic model demonstrates remarkable agreement with hydrodynamic simulations.
• The model reproduces key Ly-α forest statistics, including the flux power spectrum and cross-correlation with dark matter halos, at the percent level.
• Accuracy extends down to scales of a few Megaparsecs.

Conclusions:

• The developed model effectively bridges analytic predictions on large scales with simulation accuracy on small scales.
• This work provides essential tools for field-level inference from Ly-α forest data and simulation-based cosmological priors.
• The model is timely for maximizing the scientific return from instruments like the Dark Energy Spectroscopic Instrument (DESI).