2021ApJ...914...66N

In preparation for the tomography study of the intergalactic medium (IGM) by Subaru Prime Focus Spectrograph (PFS) survey and other large future telescopes such as TMT/ELT/GMT, we present the results of our pilot study on Lyα forest and IGM tomography statistics using the GADGET3-OSAKA cosmological smoothed particle hydrodynamical simulation. Our simulation includes models for star formation and supernova feedback, which enables more realistic cross-correlation studies between galaxies, neutral hydrogen (H I), and metals in circumgalactic and intergalactic medium. We create a light-cone data set at z = 2-3 from our simulations and generate mock Lyα forest data. As a first step, in this paper, we focus on the distribution of H I and galaxies, and present statistical results on 1D flux probability distribution function, 1D power spectrum, flux contrast versus impact parameter, and H I-galaxy cross-correlations. Our results show overall agreement with current observational data, with some interesting discrepancies on small scales that are due to either feedback effects or varying observational conditions. Our simulation shows stronger H I absorption with decreasing transverse distance from galaxies. We find that massive galaxies with M_* >= 10¹⁰ M_☉ contribute strongly to the flux contrast signal, and that lower-mass galaxies with M_* ∼ 10⁸-10¹⁰ M_☉ tend to dilute the flux contrast signal from massive galaxies. On large scales, the average flux contrast smoothly connects to the IGM level, supporting the concordance Λ cold dark matter model. We also find an increase in the H I absorption toward the center of a protocluster.