The dynamic centres of infrared-dark clouds and the formation of cores
The dynamic centres of infrared-dark clouds and the formation of cores
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红外暗云的动力中心和核心的形成
DOI：
10.1093/mnras/stae030
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发表时间：
2024
影响因子：
4.8
通讯作者：
Rigby A
中科院分区：
文献类型：
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作者：
Rigby A
大质量恒星对星系中星际介质的演化有着巨大的影响，因此了解它们是如何形成的非常重要。我们研究了七个具有不同质量和形态的红外暗云（irdc）样本中的中心团块。我们利用北方扩展毫米波阵列（NOEMA）和theIRAM30m望远镜的1 pc尺度观测，追踪了2.8 mm连续体的致密核心，以及C18O， HCO+， HNC和N2H+(J= 1-0)的气体运动学。我们用阿塔卡马大型毫米/亚毫米阵列（ALMA）在2.9 mm处观测到的6个irdc补充了我们的连续样品，并研究了核心和团块尺度性质之间的关系。我们开发了一个全自动的多速度组件超精细线拟合代码，称为dmwydyn，我们使用它来跟踪N2H+(1-0)中的致密气体运动学，揭示高度复杂和动态的团块内部。我们发现，秒差尺度的团块质量是驱动演化的最重要因素；更大的团块能够将更多的质量集中到它们最大的核心中——对数正态分布的效率约为9%——此外还包含最活跃的气体。大多数大质量地核内的线宽分布与周围气体相似，这表明它们不是动态解耦的，而是类似的混沌。之前的一些研究表明，团块正在全球坍缩；在这种情况下，观察到的团块中心的运动学将是重力驱动的质量流入的直接结果，随着团块的演变，质量流入变得越来越复杂，这反过来导致其核心群体的质量增长混乱。
High-mass stars have an enormous influence on the evolution of the interstellar medium in galaxies, so it is important that we understand how they form. We examine the central clumps within a sample of seven infrared-dark clouds (IRDCs) with a range of masses and morphologies. We use 1-pc-scale observations from the Northern Extended Millimeter Array (NOEMA) and theIRAM30m telescope to trace dense cores with 2.8-mm continuum, and gas kinematics in C18O, HCO+, HNC, and N2H+(J= 1–0). We supplement our continuum sample with six IRDCs observed at 2.9 mm with the Atacama Large Millimeter/submillimeter Array (ALMA), and examine the relationships between core- and clump-scale properties. We have developed a fully automated multiple-velocity component hyperfine line-fitting code calledmwydynwhich we employ to trace the dense gas kinematics in N2H+(1–0), revealing highly complex and dynamic clump interiors. We find that parsec-scale clump mass is the most important factor driving the evolution; more massive clumps are able to concentrate more mass into their most massive cores – with a log-normally distributed efficiency of around 9 per cent – in addition to containing the most dynamic gas. Distributions of linewidths within the most massive cores are similar to the ambient gas, suggesting that they are not dynamically decoupled, but are similarly chaotic. A number of studies have previously suggested that clumps are globally collapsing; in such a scenario, the observed kinematics of clump centres would be the direct result of gravity-driven mass inflows that become ever more complex as the clumps evolve, which in turn leads to the chaotic mass growth of their core populations.