A homogeneous sample of sub-damped Lyman α systems – II. Statistical, kinematic and chemical properties
A homogeneous sample of sub-damped Lyman α systems – II. Statistical, kinematic and chemical properties
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亚阻尼莱曼 α 系统的均质样本 – II。
DOI：
10.1046/j.1365-8711.2003.06952.x
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发表时间：
2003
影响因子：
4.8
通讯作者：
UK.
中科院分区：
文献类型：
--
作者：
C. Péroux;M. Dessauges;S. D’odorico;Tae Sun Kim;Richard G. McMahon Osservatorio di Trieste;I. E. G. Observatory;G. I. F. Astronomy;Cambridge;UK.
在类星体光谱中观测到的N（HI）> 2 × 1020原子cm - 2的阻尼莱曼α系统（DLAs），使我们能够在宇宙学尺度上定量宇宙的化学成分。这样的研究可以扩展到更低的柱密度，在亚DLA范围内[10 1 9 3.5。在本文中，我们使用一个均匀的样品，从欧洲南方天文台（ESO）的紫外-可见中阶梯光谱仪（UVES）文件中提出的档案，以确定观测的第一次列密度分布的形状，f（N），下降到N（H I）= 10 1 9原子cm - 2。结果与Peroux等人的预测吻合得很好。我们还提出了本次调查的子DLAs，这似乎是略有不同的DLAs的运动学和聚类特性。我们比较了低和高电离过渡宽度，并发现子DLAs的属性大致跨越DLAs的参数空间。我们还发现，在金属线的速度宽度较大的系统的金属丰度增加的提示，虽然这一结果的统计意义是低的。然后，我们分析了这个样品的化学成分，并从文献中收集了72个DLAs的丰度。如前所述，这些系统的[Fe/H]追踪的单个金属丰度随着红移而温和地演变。此外，我们分析了H I柱密度加权平均丰度，这被认为是宇宙金属丰度的指标。虽然数量统计是有限的，在目前的样本，结果表明，这个数量的一个稍微强的演变在亚DLA范围。这种效应在z < 2时占主导地位，观察到的大部分演化都在这个红移范围内。观测参数支持这一假设，即我们探测的亚DLA范围内的演变不是由于其较低的尘埃含量。因此，这些系统可能与不同类别的物体有关，这些物体可以更好地追踪宇宙的整体化学演化。最后，结合文献中的DLA测量，我们给出了亚DLA的[Si/Fe]、[O/Fe]、[C/Fe]和[Al/Fe]丰度比。亚DLAs中的元素比与DLAs中的元素比相当。很难解释观测到的数值是核合成的影响，还是由于不同的尘埃损耗。的金属丰度进行了比较，以提供约束的类星体吸收体的形态与两套不同的模型的星系演化。
Damped Lyman a systems (DLAs), with N(HI) > 2 x 10 2 0 atom cm - 2 , observed in the spectra of quasars have allowed us to quantify the chemical content of the Universe over cosmological scales. Such studies can be extended to lower column densities, in the sub-DLA range [10 1 9 3.5. In this paper, we use a homogeneous sample of sub-DLAs from the European Southern Oberservatory (ESO) Ultraviolet-Visual Echelle Spectrograph (UVES) archives presented in Paper I, to determine observationally for the first time the shape of the column density distribution, f(N), down to N(H I) = 10 1 9 atom cm - 2 . The results are in good agreement with the predictions from Peroux et al. We also present the kinematic and clustering properties of this survey of sub-DLAs, which appear to be marginally different from the DLAs. We compare low- and high-ionization transition widths and find that the properties of the sub-DLAs span roughly the parameter space of DLAs. We also find hints of an increase of metallicity in systems with larger velocity widths in the metal lines, although the statistical significance of this result is low. Then we analyse the chemical content of this sample in conjunction with a compilation of abundances from 72 DLAs taken from the literature. As previously reported, the individual metallicities traced by [Fe/H] of these systems evolve mildly with redshift. Moreover, we analyse the H I column-density-weighted mean abundance, which is believed to be an indicator of the metallicity of the Universe. Although the number statistics is limited in the current sample, the results suggest a slightly stronger evolution of this quantity in the sub-DLA range. The effect is predominant at z < 2 and most of the evolution observed lies in this redshift range. Observational arguments support the hypothesis that the evolution we probe in the sub-DLA range is not due to their lower dust content. Therefore, these systems might be associated with a different class of objects, which better trace the overall chemical evolution of the Universe. Finally, we present abundance ratios of [Si/Fe], [O/Fe], [C/Fe] and [Al/Fe] for sub-DLAs in conjunction with DLA measurements from the literature. The elemental ratios in sub-DLAs are comparable with those from DLAs. It is difficult to decipher whether the observed values are the effect of nucleosynthesis or are due to differential dust depletion. The metallicities are compared with two different sets of models of galaxy evolution in order to provide constraints on the morphology of quasar absorbers.