How the Milky Way ticks: comprehending complexity in the interstellar medium, from ethereal wisps to dense structures at the onset of star formation

银河系如何运行：理解星际介质的复杂性，从空灵的缕缕到恒星形成开始时的致密结构

• 批准号: 6843-2013
• 负责人: Martin, Peter
• 金额: $ 3.79万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633425
• 关键词: How; Milky; Way; ticks; comprehending

I want to understand how our Milky Way Galaxy ticks, why, unlike in other galaxies, there is still an interstellar medium (ISM) in which stars are continually forming. This requires a broad program to understand Galactic ecology, the cycling of the ISM from the diffuse atomic phase to dense molecular clouds, the sites of star formation, and back. So complex is the ISM that comprehending the structure and dynamics at the key stages, from ethereal wisps to dense structures at the onset of star formation, requires exploitation and synthesis of all available multiwavelength data. I am working with international teams at a new frontier revolutionizing this field, in the submillimetre with the Herschel and Planck satellites which image thermal emission by small interstellar dust particles tracing the gas. Deciphering the fascinating evolution of dust becomes necessary because dust is implicated in so many key interstellar processes. An exciting new insight from Planck is polarization, probing the important role of the interstellar magnetic field in the life cycle. A key question that will be addressed is the state of the ISM in the hitherto elusive earliest stages of star formation, before substantial accretion and nuclear ignition reveal new stars. The compact structures that we can now detect in the submillimetre are cold condensations, starless cores. How these form and the dependence on environment are still unkown, but progess can be made by relating the onset and efficiency of core formation, and their mass function, to the larger-scale high column density structures like filaments, and tracing the thermal and dynamical state with molecular line probes. At high Galactic latitudes we see the return cycle, the interstellar cirrus, fairly local gas and dust in the disk, as well as intermediate velocity clouds, part of the Galactic fountain, material thrust out of the disk and circulating in the halo. Comprehending the turbulent structure of the cirrus is essential to learning how molecular clouds form, and has another huge impact because cirrus is a polarized foreground that must be removed to reach the cosmological goals of studies of the cosmic microwave and infrared backgrounds.

我想了解我们的银河系是如何运转的，为什么与其他星系不同的是，星际介质(ISM)仍然存在，恒星在其中不断形成。这需要一个广泛的计划来理解银河系生态学，即ISM从扩散原子阶段到致密分子云的循环，恒星形成的地点，以及回来。ISM是如此复杂，以至于理解关键阶段的结构和动力学，从虚幻的一缕到恒星形成之初的致密结构，需要开发和合成所有可用的多波长数据。我正在一个新的前沿领域与国际团队合作，用赫歇尔和普朗克卫星拍摄跟踪气体的星际小尘埃粒子的热发射，在亚毫米范围内给这一领域带来革命性的变化。破译尘埃迷人的演化是必要的，因为尘埃牵涉到如此多的关键星际过程。来自普朗克的一个令人兴奋的新见解是极化，他探索了星际磁场在生命周期中的重要作用。要解决的一个关键问题是，在实质性吸积和核点火揭示新恒星之前，ISM在恒星形成的早期阶段处于何种状态。我们现在可以在亚毫米级探测到的致密结构是冷凝聚，没有恒星的核心。这些形式和对环境的依赖尚不清楚，但通过将核心形成的开始和效率以及它们的质量函数与更大范围的高柱密度结构(如细丝)联系起来，并用分子线探针追踪热状态和动力学状态，可以取得进展。在银河系高纬度，我们可以看到返回周期，星际卷云，相当局部的气体和尘埃，以及中速云，银河系喷泉的一部分，物质从盘中喷出，在光晕中循环。了解卷云的湍流结构对于了解分子云是如何形成的至关重要，而且还有另一个巨大的影响，因为卷云是一种极化前景，必须去除它才能达到宇宙微波和红外背景研究的宇宙学目标。