Forecasting constraints on the high-z mfp from the Lyman-α forest flux auto-correlation function

The auto-correlation function of the Lyman-α (Lyα) forest flux from high-z quasars can statistically probe the physical state of the intergalactic medium (IGM) just after the epoch of reionization. This correlation function is sensitive to all physical scales of the Lyα forest flux, enabling it to constrain the mean free path (mfp) of ionizing photons. A recent measurement of the mfp at z = 6 reported a smaller value than expected from lower z studies. We investigate the precision with which the auto-correlation function can constrain the mfp from 5.4 ≤ z ≤ 6 in bins of Δ z = 0.1 using mock datasets generated from cosmological hydrodynamical simulations with semi-numerical models of the UV background. When considering 100 realizations of a mock dataset of 20 quasars, we find the median width of the error bars ranges from 131%–228% of the measurement for low resolution data and from 104%–194% for high-resolution data across the different redshift bins. This result provides the opportunity for a measurement of the Lyα auto-correlation function to independently constrain the evolution of the mfp at high-z.