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arXiv 1201.0184astro-ph.SR
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年轻天体Ne II发射的高分辨光谱学

High resolution spectroscopy of Ne II emission from young stellar objects

G. G. Sacco, E. Flaccomio, I. Pascucci, F. Lahuis, B. Ercolano, J. H. Kastner, G. Micela, B. Stelzer, M. Sterzik

备注：
35 pages, 7 figures, accepted for publication on ApJ
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摘要：

限制星周盘气体成分的空间和热结构对于理解恒星和行星形成至关重要。模型预测，斯皮策望远镜在年轻恒星天体中探测到的12.81 μm处的[Ne II]线追踪了盘气体及其对高能辐射的响应，但这种[Ne II]发射也可能起源于强大外流中的激波。为了区分这些潜在的起源中红外[Ne II]发射和限制磁盘模型，我们观察了32个年轻的恒星物体使用高分辨率（R~30000）中红外光谱仪VISIR在VLT。我们在12个天体中探测到了12.81 μm [Ne II]谱线，这是使用高空间和光谱分辨率摄谱仪在年轻恒星天体中探测到这条谱线的三倍。我们得到了以下主要结果：a）在I类天体中，斯皮策望远镜观测到的[Ne II]辐射主要来自于距离恒星20-40 AU的气体，在那里，氖很可能是由原恒星流出的激波电离的。b）在过渡和过渡前的盘中，大部分的辐射都局限于内盘，距离中心恒星20-40 AU。c）对谱线轮廓的详细分析表明，在过渡和过渡前的星盘中，谱线相对于恒星速度有轻微的蓝移（2-12 km/s{^-1}），谱线宽度与星盘倾角直接相关，正如预期的那样，如果辐射是由星盘风引起的。d）EUV/X射线照射的圆盘模型很好地再现了观察到的线宽和圆盘倾角之间的关系，但低估了线的蓝移。

英文摘要：

Constraining the spatial and thermal structure of the gaseous component of circumstellar disks is crucial to understand star and planet formation. Models predict that the [Ne II] line at 12.81 μm detected in young stellar objects with Spitzer traces disk gas and its response to high energy radiation, but such [Ne II] emission may also originate in shocks within powerful outflows. To distinguish between these potential origins for mid-infrared [Ne II] emission and to constrain disk models, we observed 32 young stellar objects using the high resolution (R~30000) mid-infrared spectrograph VISIR at the VLT. We detected the 12.81 μm [Ne II] line in 12 objects, tripling the number of detections of this line in young stellar objects with high spatial and spectral resolution spectrographs. We obtain the following main results: a) In Class I objects the [Ne II] emission observed from Spitzer is mainly due to gas at a distance of more than 20-40 AU from the star, where neon is, most likely, ionized by shocks due to protostellar outflows. b) In transition and pre-transition disks, most of the emission is confined to the inner disk, within 20-40 AU from the central star. c) Detailed analysis of line profiles indicates that, in transition and pre-transition disks, the line is slightly blue-shifted (2-12 km s{^-1}) with respect to the stellar velocity, and the line width is directly correlated with the disk inclination, as expected if the emission is due to a disk wind. d) Models of EUV/X-ray irradiated disks reproduce well the observed relation between the line width and the disk inclination, but underestimate the blue-shift of the line.

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