The Lyman-α forest of high redshift quasars is a powerful probe of the late stages of the Epoch of Reionization (EoR), particularly through the presence of Gunn-Peterson troughs. These troughs span a broad range of lengths (up to 100 Mpc), suggesting large-scale coherent structures in the intergalactic medium. We aim to gain insight into the presence, extent, and magnitude of correlations in the Lyman-α forest at 5 5. 3, extending at least tens of Mpc and strongly increasing with redshift. Our results suggest a redshift-dependent correlation length, from L 26. 53\, (68. 47) Mpc at 1-σ (2-σ) limit at z = 5. 0 to L = 252. 72^+272. 61-₄₁. ₆₁ Mpc at z = 6. 1. In contrast, all simulation models predict shorter correlation lengths (200 Mpc scales at z=6 indicates that cosmological simulations should be larger than this scale to adequately sample the Lyman-α forest. Despite implementing a fluctuating UVB and numerous neutral islands at z<6, our fiducial SCRIPT-based simulation fails to reproduce the large-scale correlations. It may be that those ingredients are necessary, but not sufficient, to understanding the unfolding of the EoR.
Spina et al. (Wed,) studied this question.