This paper systematically investigates the comoving megaparsec-scale intergalactic medium (IGM) environment around galaxies traced by the Lyα forest. Using our cosmological hydrodynamic simulations, we investigate the IGM–galaxy connection at z = 2 by two methods: (i) cross-correlation analysis between galaxies and the fluctuation of Lyα forest transmission (δ _F) and (ii) comparison of the overdensity of neutral hydrogen (H i) and galaxies. Our simulations reproduce observed cross-correlation functions (CCFs) between Lyα forest and Lyman-break galaxies. We further investigate the variation of the CCF using subsamples divided by dark matter halo mass (M _DH), galaxy stellar mass (M _⋆), and star formation rate (SFR) and find that the CCF signal becomes stronger with increasing M _DH, M _⋆, and SFR. The CCFs between galaxies and gas density fluctuation are also found to have similar trends. Therefore, the variation of δ _F–CCF depending on M _DH, M _⋆, and SFR is due to varying gas densities around galaxies. We find that the correlation between galaxies and the IGM H i distribution strongly depends on M _DH as expected from linear theory. Our results support the ΛCDM paradigm, confirming a spatial correlation between galaxies and IGM H i, with more massive galaxies being clustered in higher-density regions.

本文系统地研究了由 Ly α森林追踪的星系周围共同移动的百万秒差距尺度的星系间介质 (IGM) 环境。使用我们的宇宙流体动力学模拟，我们通过两种方法研究了z = 2处的 IGM-星系连接：（i）星系之间的互相关分析和 Ly α森林传输（δ _F）的波动和（ii）超密度的比较中性氢 (H i ) 和星系。我们的模拟再现了 Ly α森林和 Lyman-break 星系之间观察到的互相关函数 (CCF) 。我们使用子样本除以暗物质晕质量（M _DH )、星系恒星质量 ( M _⋆ ) 和恒星形成率 (SFR) 并发现 CCF 信号随着M _DH、M _⋆和 SFR 的增加而变得更强。星系之间的CCF和气体密度波动也被发现具有相似的趋势。因此，δ _F –CCF的变化取决于M _DH、M _⋆和 SFR 是由于星系周围气体密度的变化。我们发现星系和 IGM H i分布之间的相关性强烈依赖于M _DH正如线性理论所预期的那样。我们的结果支持 ΛCDM 范式，证实了星系和 IGM H i之间的空间相关性，更大质量的星系聚集在更高密度的区域。