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arXiv 1706.08720astro-ph.GA
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朝向三个斯皮策泡S116、S117和S118的分子云:形成三个\HII \区域和一个10-pc尺度分子空腔的云-云碰撞的证据

Molecular clouds toward three Spitzer bubbles S116, S117 and S118: Evidence for the cloud-cloud collision which formed the three \HII \ regions and a 10-pc scale molecular cavity

Yasuo Fukui, Akio Ohama, Mikito Kohno, Kazufumi Torii, Shiji Fujita, Yusuke Hattori, Atsushi Nishimura, Hiroaki Yamamoto, Kengo Tachihara

摘要:

我们对三个斯皮策泡S116,S117和S118进行了分子线研究,这三个泡显示了高质量恒星的活跃形成。我们发现分子气体由两个速度差为{ $\sim 5$ \kms }的组分组成。其中一个是小云团,具有{ $-63$ \kms }的典型速度,另一个是大云团,具有$-58$ \kms的典型速度。大云团有一个近似圆形的强度低压,其大小与小云团相似。我们提出了一个解释,腔是由两个云之间的碰撞和碰撞压缩气体成一个致密的层沿小云的西部边缘拉长。在这种情况下,O型星,包括那些在三个斯皮策泡形成的界面层压缩的碰撞。通过假设云的相对运动相对于视线的倾斜度为\timeform{45D},我们估计碰撞在过去的100万年中以$\sim$ 10 \kms的相对速度持续。在S116--117--118系统中,\HII \区域位于腔的外部。这种形态归因于大云的密度约束分布,这使得\HII \区域更容易向大云的外部而不是空腔内部扩展。目前的情况证明,云-云碰撞产生的空腔没有O星反馈的作用,并建议碰撞压缩层是高度的粘性。

英文摘要:

We carried out a molecular line study toward the three Spitzer bubbles S116, S117 and S118 which show active formation of high-mass stars. We found molecular gas consisting of two components with velocity difference of {$\sim 5$ \kms}. One of them, the small cloud, has typical velocity of {$-63$ \kms} \ and the other, the large cloud, has that of $-58$ \kms. The large cloud has a nearly circular intensity depression whose size is similar to the small cloud. We present an interpretation that the cavity was created by a collision between the two clouds and the collision compressed the gas into a dense layer elongated along the western rim of the small cloud. In this scenario, the O stars including those in the three Spitzer bubbles were formed in the interface layer compressed by the collision. By assuming that the relative motion of the clouds has a tilt of \timeform{45D} to the line of sight, we estimate that the collision continued over the last 1 Myr at relative velocity of $\sim$10 \kms. In the S116--117--118 system the \HII \ regions are located outside of the cavity. This morphology is ascribed to the density-bound distribution of the large cloud which made the \HII \ regions more easily expand toward the outer part of the large cloud than inside of the cavity. The present case proves that a cloud-cloud collision creates a cavity without an action of O star feedback, and suggests that the collision-compressed layer is highly filamentary.

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