The physics and chemistry of low-mass cores

低质量分子云核心是类太阳恒星的诞生地。因此，要彻底了解恒星的形成，就需要详细了解它们的初始性质。附近的小而孤立的云，如博克球，是研究这些恒星形成核心的物理和化学特性的理想实验室，因为它们不受更密集的恒星形成区域中存在的复杂影响，而且相对容易建立模型。尽管这种方法相对简单，但我们仍然缺乏对这种核的两个基本物理参数的可靠测量：温度和密度。这两个参数调节了化学和动力学演化以及随后的引力坍缩和破碎。来自赫歇尔项目“EPOS”的数据使我们第一次能够直接测量14个孤立恒星形成核心样本的温度和密度结构。为了测量气粒耦合过程以及湍流和磁支持的作用，我们已经获得了一组不同CO同位素和N2H+的互补分子线图，并提出了至少对NH3， CS， HCO+的进一步观测。这些观测结果结合在一起，提供了一个独特的机会，以一种前所未有的方式，模拟星际介质中密度最大和最冷的恒星形成单元的化学和动力学状态。我们的目标是推导出一种新的相干建模方法，在这种方法中，从尘埃连续体数据中得到的高精度物理结构可以作为最先进的化学模型的独立输入，这反过来又允许我们约束这种恒星形成核心的化学演化。

Low–mass molecular cloud cores are the birthplaces of solar–type stars. Therefore, a thorough understanding of star–formation requires detailed knowledge of their initial properties. Nearby, small and isolated clouds, like Bok globules, are ideal laboratories for studying the physical and chemical properties of such star–forming cores because they are free from the complicating effects present in more clustered star–forming regions and are relatively straight–forward to model. Despite this relative simplicity, we still lack robust measurements of two fundamental physical parameters of such cores: temperature and density. These two parameters regulate the chemical and dynamical evolution and the subsequent gravitational collapse and fragmentation. The data from our Herschel project “EPOS” allow us for the first time to directly measure the temperature and density structure in a sample of 14 isolated star–forming cores. In order to measure gas–grain coupling processes and the role of turbulence and magnetic support, we have already acquired a set of complementary molecular line maps of different CO isotopes and N2H+ and propose further observations of at least NH3, CS, HCO+. When combined, these observations present the unique opportunity to model, in an unprecedented way, the chemical and dynamical state of the densest and coldest star–forming units in the interstellar medium. Our aim is to derive a new — coherent — modeling approach in which the highly accurate physical structure derived from the dust continuum data serves as independent input for the state–of–the–art chemical models, which in turn allow us to constrain the chemical evolution of such star–forming cores.