AI 中文总结
研究通过识别投影特殊速度梯度功率谱中的声学特征，利用玩具模型和线性理论，结合模拟方法及对z = 4.2 - 5.0通量功率谱的测量，首次直接测得高红移下宇宙间压力平滑尺度，为恢复热历史观测计划奠基。
AI 中文摘要
再电离时代在宇宙的热历史中留下了可探测的印记。特别是，快速电离前沿掠过宇宙网中的冷气体，使气体压力过大，导致了由于气体的流体动力学响应而产生的压力平滑这一公认现象。尽管过去几十年已从莱曼α森林的功率谱中间接测量了这种效应，但直接测量与该物理过程相关的典型尺度的例子却很少。这项工作在投影特殊速度梯度η的功率谱中识别出一个声学特征。通过玩具模型和线性理论，表明该声学特征可能与压力平滑尺度密切相关。在k = 0.1 - 1 s/km的莱曼α森林的小尺度通量功率谱上也印刻了相同尺度的特征。为模拟开发的一种方法应用于z = 4.2 - 5.0时通量功率谱的最新测量，以提供高红移下压力平滑尺度的首次直接测量，即λ_p(z = 4.2)>33.78 ckpc(1σ)，λ_p(z = 4.6)=32.36±8.35 ckpc和λ_p(z = 5.0)=31.27±18.28 ckpc。这项概念验证研究为未来旨在通过对莱曼α森林的小尺度观测来恢复热历史的观测计划铺平了道路。
英文摘要
The epoch of reionization leaves detectable imprints in the thermal history of the Universe. In particular, the fast ionization fronts passing over cold gas in the cosmic web overpressurize the gas, leading to the well-established phenomenon of pressure smoothing due to the hydrodynamic response of the gas. Although the effect has been indirectly measured from the power spectra of the Lyman-$α$ forest over the past decades, very few examples exist of directly measuring the typical scale associated with this physical process. This work identifies an acoustic feature in the power spectrum of the projected peculiar velocity gradient $η$. Using toy models and linear theory, this work shows that the acoustic feature is likely strongly associated with the pressure smoothing scale. A feature at the same scale is imprinted on the small-scale flux power spectrum of the Lyman-$α$ forest at $k=0.1-1\;\mathrm{s/km}$. A methodology developed for the simulations is applied to the latest measurements of the flux power spectra at $z=4.2-5.0$ to provide the first direct measurements of the pressure smoothing scale at high redshifts, $λ_p(z=4.2) > 33.78\;\mathrm{ckpc}\;(1σ)$, $λ_p(z=4.6) = 32.36\pm8.35\;\mathrm{ckpc}$ and $λ_p(z=5.0)=31.27\pm18.28\;\mathrm{ckpc}$. This proof-of-concept study paves the way for future observational programs aimed at recovering the thermal history using small-scale observations of the Lyman-$α$ forest.
Comments15 pages, 11 figures
