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arXiv 0908.1574astro-ph.CO
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来自斯隆数字巡天II的中性气体宇宙学质量密度的演化-数据发布7

Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7

P. Noterdaeme, P. Petitjean, C. Ledoux, R. Srianand

摘要:

我们目前的阻尼莱曼α(DLA)系统在斯隆数字巡天II(SDSS),数据发布7搜索的结果。我们使用一个全自动的程序来识别DLAs,并推导出它们的列密度。将根据先前在SDSS中搜索DLA的结果检查该过程。我们讨论的协议和分歧,并显示我们的程序的鲁棒性。对于每个系统,我们获得了准确的测量吸收体的红移,HI柱密度和相关的金属吸收线的等效宽度,没有任何人为干预。我们发现1426个吸收体具有2.15 < z < 5.2,log N(HI)>=20,其中937个系统的log N(HI)>= 20.3。这是有史以来最大的DLA样本,通过本文的电子版提供给科学界。在调查过程中,我们发现了迄今为止已知的具有最高HI柱密度的中间DLA,log N(HI)=22.0+/-0.1。该单一系统对现在以高精度测量的N(HI)频率分布的高端提供了强约束。我们表明,在类星体光谱的蓝端的DLA的存在下,可以导致重要的系统误差,并提出了一种方法来避免它们。这对测量z~2.2的中性气体的宇宙质量密度有重要的影响,因此对我们理解过去100亿年的星系演化也有重要的影响。[截短]

英文摘要:

We present the results of a search for damped Lyman-alpha (DLA) systems in the Sloan Digital Sky Survey II (SDSS), Data Release 7. We use a fully automatic procedure to identify DLAs and derive their column densities. The procedure is checked against the results of previous searches for DLAs in SDSS. We discuss the agreements and differences and show the robustness of our procedure. For each system, we obtain an accurate measurement of the absorber's redshift, the HI column density and the equivalent width of associated metal absorption lines, without any human intervention. We find 1426 absorbers with 2.15 < z < 5.2 with log N(HI)>=20, out of which 937 systems have log N(HI)>= 20.3. This is the largest DLA sample ever built, made available to the scientific community through the electronic version of this paper. In the course of the survey, we discovered the intervening DLA with highest HI column density known to date with log N(HI)=22.0+/-0.1. This single system provides a strong constraint on the high-end of the N(HI) frequency distribution now measured with high accuracy. We show that the presence of a DLA at the blue end of a QSO spectrum can lead to important systematic errors and propose a method to avoid them. This has important consequences for the measurement of the cosmological mass density of neutral gas at z~2.2 and therefore on our understanding of galaxy evolution over the past 10 billion years. [truncated]

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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