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arXiv 1005.2867astro-ph.GA
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嵌入低质量年轻恒星的c2d Spitzer IRS光谱:气相发射线

c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines

Fred Lahuis, Ewine F. van Dishoeck, Jes K. Jørgensen, Geoffrey A. Blake, Neal J. Evans

摘要:

对43颗位于恒星形成区附近的低质量年轻恒星的H2、H2O和各种原子的中红外气相发射谱线进行了观测。这些源是从斯皮策的“核心到核心”(c2 d)遗留计划中选择的。嵌入式原恒星的环境在其物理结构(包层、外流、喷流、原恒星盘)和发生的物理过程(吸积、紫外线和/或X射线照射、通过慢速和快速冲击激发)方面都是复杂的。Spitzer-IRS光谱的空间分辨是一个关键问题。一个最佳的提取方法是用来分离空间未解决的(紧凑,高达几百AU)和空间解决(扩展,1000 AU或更多)从IRS光谱发射。结果与c2 d磁盘样本和文献PDR和冲击模型,以解决的物理性质的来源进行了比较。观察到紧凑和扩展的发射特征。通过纯转动H_2S(0)、S(1)和S(2)线观察到的暖(Texfew 100 K)H_2和[SI] 25 μ发射主要在扩展分量中观察到。[S I]是唯一针对真正嵌入的源而不是磁盘观察到的。另一方面,热(Tex>700 K)H2,主要通过S(4)线观察到,[Ne II]发射主要在致密组分中观察到。[Fe在两个空间分量中都观察到[Si II]和[Si II]线。在某些源的致密组分中发现了热H2O发射。在大于等于1000 AU的尺度上观测到的辐射是PDR辐射的特征,可能起源于恒星风和嵌入的年轻恒星喷流所产生的残余包层中的外流空腔。沿流出壁的弱激波也会起作用。紧凑的排放可能是混合的起源,包括光学厚拱盘和/或喷流/流出排放的原恒星物体。

英文摘要:

A survey of mid-IR gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer "Cores to Disks" (c2d) legacy program. The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. A key point is to spatially resolve the emission in the Spitzer-IRS spectra. An optimal extraction method is used to separate both spatially unresolved (compact, up to a few 100 AU) and spatially resolved (extended, 1000 AU or more) emission from the IRS spectra. The results are compared with the c2d disk sample and literature PDR and shock models to address the physical nature of the sources. Both compact and extended emission features are observed. Warm (Tex few 100 K) H2, observed through the pure rotational H2 S(0), S(1) and S(2) lines, and [S I] 25 mu emission is observed primarily in the extended component. [S I] is observed uniquely toward truly embedded sources and not toward disks. On the other hand hot (Tex>700 K) H2, observed primarily through the S(4) line, and [Ne II] emission is seen mostly in the compact component. [Fe II] and [Si II] lines are observed in both spatial components. Hot H2O emission is found in the compact component of some sources. The observed emission on >=1000 AU scales is characteristic of PDR emission and likely originates in the outflow cavities in the remnant envelope created by the stellar wind and jets from the embedded young stars. Weak shocks along the outflow wall can also contribute. The compact emission is likely of mixed origin, comprised of optically thick circumstellar disk and/or jet/outflow emission from the protostellar object.

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