Understanding the survival of gas within subhalos under various astrophysical processes is crucial for elucidating cosmic structure formation and evolution. We study the resilience of gas in subhalos, focusing on the impact of tidal and ram pressure stripping through hydrodynamic simulations. Our results uncover significant gas stripping primarily driven by ram pressure effects, which also profoundly influence the gas distribution within these subhalos. Notably, despite their vulnerability to ram pressure effects, the low-mass subhalos can play a pivotal role in influencing the observable characteristics of cosmic structures due to their large abundance. Specifically, we explore the application of our findings to the 21 cm forest, showing how the survival dynamics of gas in subhalos can modulate the 21 cm optical depth, a key probe for detecting minihalos in the pre-reionization era. Our previous study demonstrated that the 21 cm optical depth can be enhanced by the subhalos, but the effects of tidal and ram pressure stripping on the subhalo abundance have not been fully considered. In this work, we further investigate the contribution of subhalos to the 21 cm optical depth with hydrodynamic simulations, particularly highlighting the trajectories and fates of subhalos within mass ranges of 10^4-6 M _⊙ h ^-1 in a host halo of 10⁷ M _⊙h^-1, and subhalos within mass range of 10^4-5 M _⊙h^-1 in a host halo of 10⁶ M _⊙h^-1. Despite their susceptibility to ram pressure stripping, the contribution of abundant low-mass subhalos to the 21 cm optical depth is more significant than that of their massive counterparts primarily due to their greater abundance. We find that the 21 cm optical depth can be increased by a factor of approximately two due to the abundant low-mass subhalos. However, this enhancement is about twice as low as previously estimated in our earlier study, a discrepancy attributed to the effects of ram pressure stripping. Our work provides critical insights into the gas dynamics within subhalos in the early universe, highlighting their resilience against environmental stripping effects, and their impact on observable 21 cm signals.

中文翻译：

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气体在亚晕中的生存及其对 21 cm 森林信号的影响：来自流体动力学模拟的见解


了解气体在各种天体物理过程中在亚晕内的生存对于阐明宇宙结构的形成和演化至关重要。我们研究了亚晕中气体的弹性，重点关注通过流体动力学模拟的潮汐和柱塞压力剥离的影响。我们的结果揭示了主要由柱塞压力效应驱动的显着气体剥离，这也深刻影响了这些子晕内的气体分布。值得注意的是，尽管它们容易受到撞击压力效应的影响，但由于它们的丰度很大，低质量亚晕可以在影响宇宙结构的可观测特征方面发挥关键作用。具体来说，我们探讨了我们的发现在 21 cm 森林中的应用，展示了亚光晕中气体的生存动力学如何调节 21 cm 光学深度，这是在再电离前时代检测微光晕的关键探针。我们之前的研究表明，亚晕可以增强 21 cm 的光学深度，但潮汐和柱塞压力剥离对亚晕丰度的影响尚未得到充分考虑。在这项工作中，我们通过流体动力学模拟进一步研究了亚晕对 21 cm 光学深度的贡献，特别强调了 10 7 M_⊙^h-1 的宿主晕中 10^4-6M_⊙^h-1 质量范围内的亚晕的轨迹和命运，以及 10 6 M_⊙^h-1 的宿主晕中10^4-5M_⊙^h-1 质量范围内的亚晕.尽管它们容易受到冲压压力剥离的影响，但丰富的低质量亚晕对 21 cm 光学深度的贡献比大质量亚晕更重要，这主要是因为它们的丰度更高。 我们发现，由于丰富的低质量亚晕，21 cm 的光学深度可以增加大约两倍。然而，这种增强大约是我们之前研究中估计的两倍，这一差异归因于柱塞压力剥离的影响。我们的工作为早期宇宙中亚晕内的气体动力学提供了重要见解，突出了它们对环境剥离效应的适应能力，以及它们对可观测的 21 厘米信号的影响。