用位置-速度图隔离主要云-云碰撞的特征
Isolating signatures of major cloud-cloud collisions using position-velocity diagrams
摘要：
巨大分子云之间的碰撞是触发大质量恒星甚至超级星团形成的潜在机制。问题在于通过观察来识别这个过程并将其与其他机制区分开来。我们从以下模型中生成合成位置-速度图：云-云碰撞，沿视线的非相互作用云，具有内部辐射反馈的云和在星系盘中演变的更复杂的云，以尝试识别碰撞的独特特征。我们发现，一个广泛的桥梁功能连接两个强度峰值，空间相关，但分离的速度，是一个高速云云碰撞的签名。我们表明，宽桥功能是弹性的辐射反馈的影响，至少到2.5万年左右的第一个大质量（电离）恒星形成后。然而，对于10 km/s的碰撞，我们发现这只能从20- 30%的视角观察到。这样的宽桥特征已经在M20附近被发现，M20是一个非常年轻的大质量恒星形成区域，被鸟居等人（2011）认为是云-云碰撞的地点，也被泉等人（2014）发现在银河系外的恒星形成区域。
英文摘要：
Collisions between giant molecular clouds are a potential mechanism for triggering the formation of massive stars, or even super star clusters. The trouble is identifying this process observationally and distinguishing it from other mechanisms. We produce synthetic position-velocity diagrams from models of: cloud-cloud collisions, non-interacting clouds along the line of sight, clouds with internal radiative feedback and a more complex cloud evolving in a galactic disc, to try and identify unique signatures of collision. We find that a broad bridge feature connecting two intensity peaks, spatially correlated but separated in velocity, is a signature of a high velocity cloud-cloud collision. We show that the broad bridge feature is resilient to the effects of radiative feedback, at least to around 2.5Myr after the formation of the first massive (ionising) star. However for a head on 10km/s collision we find that this will only be observable from 20-30 per cent of viewing angles. Such broad-bridge features have been identified towards M20, a very young region of massive star formation that was concluded to be a site of cloud-cloud collision by Torii et al (2011), and also towards star formation in the outer Milky Way by Izumi et al (2014).
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