Compressing the cosmological information in one-dimensional correlations of the Lyman-α forest

Christian Pedersen, Andreu Font-Ribera, Nickolay Y. Gnedin

Submitted on 20 September 2022


Observations of the Lyman-α (Lyα) forest from spectroscopic surveys such as BOSS/eBOSS, or the ongoing DESI, offer a unique window to study the growth of structure on megaparsec scales. Interpretation of these measurements is a complicated task, requiring hydrodynamical simulations to model and marginalise over the thermal and ionisation state of the intergalactic medium. This complexity has limited the use of Lyα clustering measurements in joint cosmological analyses. In this work we show that the cosmological information content of the 1D power spectrum (P1D) of the Lyα forest can be compressed into a simple two-parameter likelihood without any significant loss of constraining power. We simulate P1D measurements from DESI using hydrodynamical simulations and show that the compressed likelihood is model independent and lossless, recovering unbiased results even in the presence of massive neutrinos or running of the primordial power spectrum.


Comment: Submitted to ApJ. 17 pages, 7 figures

Subject: Astrophysics - Cosmology and Nongalactic Astrophysics