CaII H&K类星体吸收体的尘埃损耗、化学均匀性和环境
Dust depletion, chemical uniformity and environment of CaII H&K quasar absorbers
摘要：
CaII 3934，3969吸收体，可能是阻尼莱曼α系统的一个子集，是已知的尘埃最多的类星体吸收体，在E（B-V）中的消光比其他吸收系统大一个数量级。也有证据表明CaII吸收体追踪的星系比一般的类星体吸收体有更多正在进行的恒星形成。尽管如此，人们对这些不寻常的吸收系统的细节知之甚少。在这里，我们提出了第一个高分辨率的光谱研究的19钙II类星体吸收，在范围0.6<= z_abs<=1.2，与W3934>=0.2A。它们的一般耗尽模式与银河系和麦哲伦云ISM的暖晕相的测量结果相似。粉尘消耗和α-富集的子样品的7和3个吸收器，分别使用Voigt轮廓拟合和表观光学深度技术相结合的测量。[Cr/Zn]~0.3+-0.1dex和[Si/Fe]>~0.8+-0.1dex的偏差在一个吸收体的剖面上被检测到，我们将其归因于差异性的粉尘贫化。其余的吸收剂在[Cr/Zn]中具有<0.3dex（3sigma极限）的变化，很像一般的DLA群体，尽管在我们的样品中最多尘的CaII吸收剂保持相对未探测。假设辐射场为类MW，利用中性粒子和单电离粒子的比值，可以推导出CaII吸收体中电子密度的极限，即n_e<0.1 cm ^-3。这些电子密度可能意味着氢密度足以在吸收剂中存在分子氢。Ca II吸收体样本包含了很宽的速度宽度（v_90=50- 470 km/s）和速度结构，因此需要一系列的物理模型来解释观测结果，从简单的圆盘到星系流出和合并。
英文摘要：
CaII 3934,3969 absorbers, which are likely to be a subset of damped Lyman alpha systems, are the most dusty quasar absorbers known, with an order of magnitude more extinction in E(B-V) than other absorption systems. There is also evidence that CaII absorbers trace galaxies with more ongoing star-formation than the average quasar absorber. Despite this, relatively little is known in detail about these unusual absorption systems. Here we present the first high resolution spectroscopic study of 19 CaII quasar absorbers, in the range 0.6<= z_abs<=1.2, with W3934>=0.2A. Their general depletion patterns are similar to measurements in the warm halo phase of the Milky Way and Magellanic Clouds ISM. Dust depletions and alpha-enrichments profiles of sub-samples of 7 and 3 absorbers, respectively, are measured using a combination of Voigt profile fitting and apparent optical depth techniques. Deviations in [Cr/Zn]~0.3+-0.1dex and in [Si/Fe]>~0.8+-0.1dex are detected across the profile of one absorber, which we attribute to differential dust depletion. The remaining absorbers have <0.3dex (3sigma limit) variation in [Cr/Zn], much like the general DLA population, though the dustiest CaII absorbers remain relatively unprobed in our sample. A limit on electron densities in CaII absorbers, n_e<0.1cm^-3, is derived using the ratio of neutral and singly ionised species, assuming a MW-like radiation field. These electron densities may imply hydrogen densities sufficient for the presence of molecular hydrogen in the absorbers. The CaII absorber sample comprises a wide range of velocity widths, v_90=50-470km/s, and velocity structures, thus a range of physical models for their origin, from simple discs to galactic outflows and mergers, would be required to explain the observations.
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