Narrow absorption lines complex I: one form of broad absorption line
Narrow absorption lines complex I: one form of broad absorption line
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DOI：
10.1093/mnras/stx2970
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发表时间：
2017-11
影响因子：
4.8
通讯作者：
Wei-Jian Lu;Ying-Ru Lin
中科院分区：
文献类型：
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作者：
Wei-Jian Lu;Ying-Ru Lin
我们发现，一些宽吸收线(BAL)实际上是窄吸收线(NAL)的复合体。作为对这一类型BAL的初步研究，我们通过一个典型的例子展示了这一发现。利用斯隆数字天文观测的J002710.06-094435.3(以下简称J0027-0944)的两个历时观测资料，我们发现C IV和Si IV BAL槽中至少包含4个NAL双星。通过将Si IV BAL分解为多个NAL，我们给出了以下主要结果和结论。首先，所有这些NAL在两个时期的SDSS观测之间都显示出协调变化，这表明它们都起源于类星体外流，它们的变化是由于吸收气体电离条件的全球变化。其次，由多个NAL组成的BAL表明，这种类型的BAL与固有的NAL基本相同，倾向于支持倾向模型而不是演化模型。第三，虽然C IV和Si IV BAL都起源于相同的块状流出子结构，但它们的轮廓形状不同：在较宽的速度范围内，Si IV BAL有多个吸收槽，而C IV BAL在较窄的速度范围内有P-Cygni。这可以通过SiIV{\lambda}{\lambda}1393,1402和C IV{\lambda}{\lambda}1548,1551双重态在精细结构和振子强度上的显著差异来解释。基于上述结论，我们认为，将BAL分解成NAL可以作为解决流出的块状结构的一种方法，它可以用来更多地了解块状结构的特征，并在利用高分辨率光谱和光电离模型时检验流出模型。
We discover that some of the broad absorption lines (BALs) are actually a complex of narrow absorption lines (NALs). As a pilot study of this type of BAL, we show this discovery through a typical example in this paper. Utilizing the two-epoch observations of J002710.06-094435.3 (hereafter J0027-0944) from the Sloan Digital Sky Survey (SDSS), we find that each of the C IV and Si IV BAL troughs contains at least four NAL doublets. By resolving the Si IV BAL into multiple NALs, we present the following main results and conclusions. First, all these NALs show coordinated variations between the two-epoch SDSS observations, suggesting that they all originate in the quasar outflow, and that their variations are due to global changes in the ionization condition of the absorbing gas. Secondly, a BAL consisting of a number of NAL components indicates that this type of BAL is basically the same as the intrinsic NAL, which tends to support the inclination model rather than the evolution model. Thirdly, although both the C IV and Si IV BALs originate from the same clumpy substructures of the outflow, they show different profile shapes: multiple absorption troughs for the Si IV BAL in a wider velocity range, while P-Cygni for the C IV BAL in a narrower velocity range. This can be interpreted by the substantial differences in fine structure and oscillator strength between the Si IV {\lambda}{\lambda}1393, 1402 and C IV {\lambda}{\lambda}1548, 1551 doublets. Based on the above conclusions, we consider that the decomposition of a BAL into NALs can serve as a way to resolve the clumpy structure for outflows, and it can be used to learn more about characteristics of the clumpy structure and to test the outflow model, when utilizing high-resolution spectra and photoionization model.