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

我想了解我们的银河系是如何运作的，为什么不像其他星系，仍然有一种星际介质（ISM），恒星在其中不断形成。这需要一个广泛的程序来了解银河系生态，ISM从扩散原子阶段到密集分子云的循环，恒星形成的位置，以及返回。ISM是如此复杂，以至于理解关键阶段的结构和动力学，从空灵的缕缕到恒星形成初期的密集结构，需要利用和综合所有可用的多波长数据。我正在与国际团队合作，在这个领域的一个新前沿进行革命性的研究，在亚毫米范围内使用赫歇尔和普朗克卫星，通过微小的星际尘埃颗粒追踪气体来拍摄热辐射。解读尘埃的迷人演化变得非常必要，因为尘埃与许多关键的星际过程有关。来自普朗克的一个令人兴奋的新发现是极化，探测星际磁场在生命周期中的重要作用。将解决的一个关键问题是，在大量吸积和核点火揭示新恒星之前，迄今为止难以捉摸的恒星形成早期阶段的ISM状态。我们现在能探测到的亚毫米级的致密结构是冷凝聚，没有恒星的核心。它们是如何形成的以及对环境的依赖仍然是未知的，但通过将核形成的开始和效率及其质量函数与更大规模的高柱密度结构（如细丝）联系起来，以及用分子线探针追踪热态和动力学状态，可以取得进展。在银河系高纬度地区，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，银河喷泉的一部分，从圆盘中喷出的物质在晕中循环。了解卷云的湍流结构对于了解分子云的形成是至关重要的，而且还有另一个巨大的影响，因为卷云是一个极化的前景，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。

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.