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arXiv 1502.07360astro-ph.GA
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大质量年轻恒星天体的Herschel Hi-GAL成像

Herschel Hi-GAL imaging of massive young stellar objects

F. A. Olguin, M. G. Hoare, H. E. Wheelwright, S. J. Clay, W. -J. de Wit, I. Rafiq, S. Pezzuto, S. Molinari

摘要:

我们使用Herschel Hi-GAL测量数据来确定大质量年轻恒星天体(MYSO)是否在70 $μ$ m处被分辨,并研究它们的包络密度分布。我们对l=30°和l=59°银河场中三个相对孤立的源的分析表明,这些天体在70 $μ$ m处是部分分辨的。Herschel Hi-GAL勘测数据具有高扫描速度,这使得未分辨和部分分辨的源在70 $μ$ m图像中出现拉长。我们分别分析了两个扫描方向,并检查垂直于扫描方向的强度分布。采用球对称辐射转移模型研究了星周物质分布。还包括单皿亚毫米数据,以研究不同的空间信息如何影响拟合的密度分布。最适合70 $μ$ m强度分布和SED的密度分布具有约0.5的平均指数。该指数比预期的要浅,可能是由于球形模型中未考虑到双极流出腔壁的粉尘排放。我们的结论是,二维轴对称模型和赫歇尔图像在低扫描速度需要更好地约束周围的物质分布MYSO。

英文摘要:

We used Herschel Hi-GAL survey data to determine whether massive young stellar objects (MYSOs) are resolved at 70$μ$m and to study their envelope density distribution. Our analysis of three relatively isolated sources in the l=30° and l=59° Galactic fields show that the objects are partially resolved at 70$μ$m. The Herschel Hi-GAL survey data have a high scan velocity which makes unresolved and partially resolved sources appear elongated in the 70$μ$m images. We analysed the two scan directions separately and examine the intensity profile perpendicular to the scan direction. Spherically symmetric radiative transfer models with a power law density distribution were used to study the circumstellar matter distribution. Single dish sub-mm data were also included to study how different spatial information affects the fitted density distribution. The density distribution which best fits both the 70$μ$m intensity profile and SED has an average index of ~0.5. This index is shallower than expected and is probably due to the dust emission from bipolar outflow cavity walls not accounted for in the spherical models. We conclude that 2D axisymmetric models and Herschel images at low scan speeds are needed to better constrain the matter distribution around MYSOs.

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