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首页> 外文期刊>The Astrophysical journal >A UNIFORM ANALYSIS OF THE Lyα FOREST AT z = 0-5. Ⅳ. THE CLUSTERING AND EVOLUTION OF CLOUDS AT z ≤ 1.7
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A UNIFORM ANALYSIS OF THE Lyα FOREST AT z = 0-5. Ⅳ. THE CLUSTERING AND EVOLUTION OF CLOUDS AT z ≤ 1.7

机译：z = 0-5时的Lyα森林的均匀分析。 Ⅳ。 z≤1.7时的云团和演化

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摘要

We present results on the evolution and clustering of Lyα lines at low redshift as part of our series "A Uniform Analysis of the Lyα Forest at z = 0-5." The sample analyzed in this paper contains 1298 Lyα absorption lines from 165 quasar spectra mined from the archives of the Faint Object Spectrograph on the Hubble Space Telescope (HST). Our sample extends to z ≈ 1.7, slightly higher than the sample analyzed by the HST Quasar Absorption Line Key Project. We confirm the result from the Key Project that the number density evolution of Lyα lines at low redshifts can be described by a power law that is significantly flatter than that found at high z. We find that the evolution is somewhat steeper than obtained previously. Specifically, we find γ = 0.54 +- 0.21 for lines with equivalent widths greater than 0.24 A and γ = 0.60 +- 0.14 using a variable equivalent width threshold. We find that the difference between our and Key Project results is likely attributable to different redshift coverage of the two samples. The results concerning the number density evolution are not significantly affected if one includes Lyα lines which are members of metal systems. Object-to-object fluctuations in the number of lines detected are small, indicating a high degree of uniformity in the intergalac-tic medium on large scales. We find marginal evidence that weak and strong lines undergo different evolution. We find weak clustering for Lyα lines at velocity separations ΔV ≤ 500 km s~(-1), weaker than the level predicted from an earlier analysis by Ulmer of a small subsample of the Key Project data. We see no correlations for metal system-Lyα forest or extensive metal system-Lyα forest combinations.
机译：我们介绍了低红移条件下Lyα系的进化和聚类结果，这是我们的系列“ z = 0-5处Lyα森林的均匀分析”的一部分。本文分析的样本包含来自165个类星体光谱的1298个Lyα吸收线，这些光谱来自哈勃太空望远镜（HST）上微弱物体光谱仪的档案。我们的样本扩展到z≈1.7，比HST类星吸收线关键项目分析的样本略高。我们确认了关键项目的结果，即在低红移条件下，Lyα线的数量密度演化可以用幂定律来描述，该幂定律比在高z处的幂定律要平坦得多。我们发现演化比以前获得的陡峭。具体来说，对于可变宽度大于0.24 A的等效线，使用可变等效宽度阈值，我们发现γ= 0.54±0.21。我们发现与主要项目结果之间的差异可能是由于两个样本的红移覆盖率不同所致。如果包含作为金属体系成员的Lyα线，则与数密度演化有关的结果不会受到显着影响。检测到的行数的对象间波动很小，这表明大规模的星际介质中的高度均匀性。我们发现边缘证据表明弱线和强线会经历不同的演变。我们发现速度间隔ΔV≤500 km s〜（-1）处Lyα线的弱聚类，弱于Ulmer先前对关键项目数据的一小部分子样本的分析所预测的水平。我们看不到金属系统-Lyα森林或广泛的金属系统-Lyα森林组合的相关性。

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