arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1602.05458astro-ph.GAastro-ph.CO
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一个没有CIV的高红移类星体吸收体--一个被捕获的星系外流?

A high-redshift quasar absorber without CIV - a galactic outflow caught in the act?

Anne Fox, Philipp Richter

摘要:

基于VLT/UVES获得的高信噪比、高分辨率的光谱数据,对类星体Q 0453 -423的一个红移z=2.304的亚阻尼莱曼α(sub-DLA)系统进行了详细的分析。中性氢柱密度log N(HI)=19.23,金属丰度为-1.61,由[OI/HI]表示,sub-DLA模拟了许多其他光学厚吸收体在此红移处的特性。然而,这个系统的一个非常不寻常的特征是,在中性氢吸收的红移处没有任何CIV吸收,尽管相关的光谱区域没有线混合并且具有非常高的S/N。相反,我们发现高离子吸收CIV和OVI在另一个金属吸收体中的速度超过220公里/秒的中性气体组件的redwards。我们探索的物理条件,在两个不同的吸收系统,使用多云的光电离模型。我们发现,弱电离的吸收体是密集的和金属贫,而高度电离的系统是薄的,更丰富的金属。朝向Q 0453 -423的吸收体对模仿了银河系外流的预期特征,其中高度电离的物质以高径向速度从(原)银河系气体盘中移动,其中发生恒星形成。我们讨论了我们的研究结果的背景下,CIV吸收线统计在高红移,并比较我们的结果,最近的银河风和外流模型。

英文摘要:

We present a detailed analysis of a very unusual sub-damped Lyman alpha (sub-DLA) system at redshift z=2.304 towards the quasar Q0453-423, based on high signal-to-noise (S/N), high-resolution spectral data obtained with VLT/UVES. With a neutral hydrogen column density of log N(HI)=19.23 and a metallicity of -1.61 as indicated by [OI/HI] the sub-DLA mimics the properties of many other optically thick absorbers at this redshift. A very unusual feature of this system is, however, the lack of any CIV absorption at the redshift of the neutral hydrogen absorption, although the relevant spectral region is free of line blends and has very high S/N. Instead, we find high-ion absorption from CIV and OVI in another metal absorber at a velocity more than 220km/s redwards of the neutral gas component. We explore the physical conditions in the two different absorption systems using Cloudy photoionisation models. We find that the weakly ionised absorber is dense and metal-poor while the highly ionised system is thin and more metal-rich. The absorber pair towards Q0453-423 mimics the expected features of a galactic outflow with highly ionised material that moves away with high radial velocities from a (proto)galactic gas disk in which star-formation takes place. We discuss our findings in the context of CIV absorption line statistics at high redshift and compare our results to recent galactic-wind and outflow models.

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