We derive H I column density and Doppler width distributions for a sample of Lyα clouds with 3.4 z 4.0, using a high-resolution spectrum of the quasar Q0000–26 (zem = 4.127) obtained with the Keck telescope. Simulated Lyα forest spectra with matching characteristics are analyzed similarly in order to gauge the effects of line blending/blanketing and noise in the data. The H I column density distribution, after corrections for incompleteness resulting from line blanketing, is well described by a single power-law function with index β = –1.55 ± 0.05 over the column density range of 12.6 log N 16.0. A steepening in the column density distribution at log N(H I) 14.5 may be present. The Doppler width distribution of the clouds is consistent with a Gaussian function with a mean of 23 km s–1 and a dispersion of 8 km s–1 but with a cutoff at 15 km s–1, i.e., no clouds with b 15 km s–1 are required to describe the data. While the H I column density distribution found here is consistent with that derived from similar quality data at lower redshifts, both the mean Doppler width and the cutoff value are smaller than those found at lower redshift. There is a hint for clustering in the clouds line-of-sight distribution in the velocity interval 100 Δv 160 km s–1, but the evidence is only marginal. Analyses of the proximity effect indicate a value of JLLν ~ 2 × 10–22 ergs s–1 cm–2 Hz–1 sr–1 for the mean intensity of the megagalactic UV ionizing background at z ~ 4.1, which is consistent with that expected from high-redshift quasars.
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机译：我们使用凯克望远镜获得的类星体Q0000–26（zem = 4.127）的高分辨率光谱，得出3.4 14.5时，柱密度分布可能会变陡。云的多普勒宽度分布与高斯函数一致，平均函数为23 km s-1，色散为8 km s-1，但截止值为15 km s-1，即，没有b <15的云需要km s–1来描述数据。尽管此处发现的H I列密度分布与从较低红移获得的相似质量数据得出的结果一致，但平均多普勒宽度和临界值均小于在较低红移时发现的密度。在速度间隔100 <Δv<160 km s-1中，云的视线分布有聚类的迹象，但证据仅是微不足道的。邻近效应分析表明，在z〜4.1时，银河系紫外线电离背景的平均强度为JLLν〜2×10–22 erss–1 cm–2 Hz–1 sr–1。来自高红移类星体。
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