标题： 2.2 < z < 4.2 氢Lyman-α森林中小尺度结构的测量 显示英文标题

标题： A Measurement of Small Scale Structure in the 2.2 < z < 4.2 Lyman-alpha Forest

摘要： Ly-α森林在小空间尺度上的涨落幅度对IGM的温度及其空间起伏敏感。 IGM的温度及其空间变化包含了关于氢和氦再电离的重要信息。 我们给出了来自40条z=2.2-4.2的高分辨率、高信噪比VLT光谱的小尺度结构的新测量结果。 我们将每个Ly-α森林光谱与一个适当选择的小波滤波器卷积，这使我们可以提取森林中小尺度结构的数量，作为每个光谱上位置的函数。 我们将这些测量结果与追踪超过20亿粒子的Ly-α森林高分辨率流体力学模拟进行了比较。 这种比较表明，接近宇宙平均密度的IGM温度（T_0）在z=3.4附近达到峰值，在这一点上，它在2-σ置信度下大于20,000 K。 较低红移处的温度与绝热冷却（$T_0 \propto (1+z)^2$）预期的下降一致，在z=3.4附近达到峰值温度。 在z=4.2时，我们的结果支持温度为T_0 = 15-20,000 K。然而，由于这个红移处平均透射通量的不确定性主要影响，这里T_0 = 10,000 K的较冷IGM模型仅在2-σ水平上被排除，尽管如此冷的IGM模型与z ~ 3-3.4的测量结果严重不符。 我们在数据集中覆盖的所有红移处都没有检测到IGM温度的大尺度变化。 我们测量结果最简单的解释是HeII再电离在z ~ 3.4附近完成，尽管统计不确定性仍然很大[摘要结束]。 显示英文摘要

摘要： The amplitude of fluctuations in the Ly-a forest on small spatial scales is sensitive to the temperature of the IGM and its spatial fluctuations. The temperature of the IGM and its spatial variations contain important information about hydrogen and helium reionization. We present a new measurement of the small-scale structure in the Ly-a forest from 40 high resolution, high signal-to-noise, VLT spectra at z=2.2-4.2. We convolve each Ly-a forest spectrum with a suitably chosen wavelet filter, which allows us to extract the amount of small-scale structure in the forest as a function of position across each spectrum. We compare these measurements with high resolution hydrodynamic simulations of the Ly-a forest which track more than 2 billion particles. This comparison suggests that the IGM temperature close to the cosmic mean density (T_0) peaks near z=3.4, at which point it is greater than 20,000 K at 2-sigma confidence. The temperature at lower redshift is consistent with the fall-off expected from adiabatic cooling ($T_0 \propto (1+z)^2$), after the peak temperature is reached near z=3.4. At z=4.2 our results favor a temperature of T_0 = 15-20,000 K. However, owing mostly to uncertainties in the mean transmitted flux at this redshift, a cooler IGM model with T_0 = 10,000 K is only disfavored at the 2-sigma level here, although such cool IGM models are strongly discrepant with the z ~ 3-3.4 measurement. We do not detect large spatial fluctuations in the IGM temperature at any redshift covered by our data set. The simplest interpretation of our measurements is that HeII reionization completes sometime near z ~ 3.4, although statistical uncertainties are still large [Abridged].