Probing the limits of cosmological information from the Lyman-$\hat{I}\pm$ forest 2-point correlation functions

Abstract

The standard cosmological analysis with the Ly$\hat{I}\pm$ forest relies on a continuum fitting procedure that suppresses information on large scales and distorts the three-dimensional correlation function on all scales. In this work, we present the first cosmological forecasts without continuum fitting distortion in the Ly$\hat{I}\pm$ forest, focusing on the recovery of large-scale information. Using idealized synthetic data, we compare the constraining power of the full shape of the Ly$\hat{I}\pm$ forest auto-correlation and its cross-correlation with quasars using the baseline continuum fitting analysis versus the true continuum. We find that knowledge of the true continuum enables a $\sim 10\%$ reduction in uncertainties on the Alcock-Paczyński (AP) parameter and the matter density, $\hat{I}{\text{c◯}}_{\mathrm{m}}$. We also explore the impact of large-scale information by extending the analysis up to separations of $240h^{-1}\mathrm{Mpc}$ along and across the line of sight. The combination of these analysis choices can recover significant large-scale information, yielding up to a $\sim 15\%$ improvement in AP constraints. This improvement is analogous to extending the Ly$\hat{I}\pm$ forest survey area by $\sim 40\%$.

32 pages, 9 figures, 3 tables; accepted to JCAP