The sub-damped Ly α system toward HE 0001−2340: galaxy formation at z ≈ 2
The sub-damped Ly α system toward HE 0001−2340: galaxy formation at z ≈ 2
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DOI：
10.1051/0004-6361:20042064
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发表时间：
2005-09
影响因子：
6.5
通讯作者：
P. Richter;C. Ledoux;P. Petitjean;J. Bergeron
中科院分区：
文献类型：
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作者：
P. Richter;C. Ledoux;P. Petitjean;J. Bergeron
我们详细分析了类星体HE 0001−2340（zem = 2.28）在z = 2.187的亚阻尼Ly α吸收体（sub-DLA）中的化学丰度。我们的研究是基于高分辨率（R = 45000）光谱数据的UVES仪器安装在ESO甚大望远镜（VLT）。该子DLA系统由至少25个独立的子组件组成，跨越10400 km s −1的静止框架速度范围。总中性氢柱密度为log N（H）<$19.7。检测到的物种包括C、C、N、N、O、M g、A l、A l、S i、S i、P、F e，可能还有D。F或vrel =+ 13 km s −1（相对于z = 2.187）的主要中性气体成分，我们推导出氧丰度（O/H）= −1.81 ± 0.07（1/65太阳）。其氮含量极低（（N/H）<-3。3a nd（N/O）-1.5）吸收体呈现经典的大质量星星丰度模式。我们的测量将z = 2.187的吸收体置于HE 0001−2340的系统中，具有有史以来最低的测量（N/α）比。低的（N/O）值与最初恒星产生的氮使星系际气体富集到（N/O）<$− 1.5的想法一致。在−350 km s −1附近（z = 2.187重坐标系）的最外层蓝色成分中发现了特殊的丰度，在校正电离效应后，我们观察到磷（（P/C）<$+1.5），硅（（Si/C）<$+0.6）和铝（（Al/C）<$+0.5）的显着过量。我们的研究表明，视线穿过一个或多个恒星团的气体环境，这些恒星团通过超新星喷出物局部富集了它们的星际邻居，从而产生了观测到的丰度异常。整个吸收系统的大速度分布表明，合并触发了这些团簇的形成。因此，我们可能正在观测一个在z = 2的年轻星系，它是在合并事件中形成的。
We present a detailed analysis of chemical abundances in a sub-damped Ly α absorber (sub-DLA) at z = 2.187 towards the quasar HE 0001−2340 (zem = 2.28). Our study is based on high-resolution (R ≈ 45 000) spectroscopic data from the UVES instrument installed on the ESO Very Large Telescope (VLT). This sub-DLA system consists of at least 25 individual subcomponents spanning a restframe velocity range of ∼400 km s −1 . The total neutral hydrogen column density is log N(H ) ≈ 19.7. Detected species include C ,C ,N ,N ,O ,M g ,A l ,A l ,S i ,S i ,P ,F e, and possibly D .F or the dominating neutral gas component at vrel =+ 13 km s −1 (relative to z = 2.187) we derive an oxygen abundance of (O/H) = −1.81 ± 0.07 (1/65 solar). With its extremely low nitrogen content ((N/H) < −3. 3a nd (N/O) −1.5) the absorber exhibits a classic massive star abundance pattern. Our measurements place the z = 2.187 absorber towards HE 0001−2340 among the systems with the lowest ever measured (N/α) ratios. The low (N/O) value is consistent with the idea that primary nitrogen production by the very first stars have enriched the intergalactic gas to a level of (N/O) ≈− 1.5. Peculiar abundances are found in the outermost blue components near −350 km s −1 (in the z = 2.187 restframe) where we observe significant overabundances of phosphorus ((P/C) ≈ +1.5), silicon ((Si/C) ≈ +0.6), and aluminum ((Al/C) ≈ +0.5) after correcting for the effects of ionization. Our study suggests that the line of sight passes through the gaseous environment of one or more stellar clusters that locally enriched their interstellar neighbourhood by supernova ejecta generating the observed abundance anomalies. The large velocity spread of the entire absorption system points to a merger that triggers the formation of these clusters. We thus may be observing a young galaxy at z ≈ 2 that is forming out of a merger event.