The physics and chemistry of low-mass cores

低质量分子云核是太阳型恒星的诞生地。因此，对恒星形成的透彻理解需要对其初始性质有详细的了解。附近的小而孤立的星云，如博克球体，是研究这种恒星形成核心的物理和化学性质的理想实验室，因为它们不受更多星团形成区域中存在的复杂效应的影响，而且建模相对简单。尽管相对简单，我们仍然缺乏对这类地核的两个基本物理参数的可靠测量：温度和密度。这两个参数控制着化学和动力学演化以及随后的引力崩塌和碎裂。来自我们的赫歇尔计划“EPOS”的数据首次使我们能够直接测量14个孤立恒星形成核心的温度和密度结构。为了测量气粒耦合过程以及湍流和磁支撑的作用，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NH3，CS，HCO+的进一步观察。这些观测结合在一起，为以前所未有的方式模拟星际介质中密度最大、最冷的恒星形成单元的化学和动力学状态提供了独特的机会。我们的目标是得出一种新的相干建模方法，在这种方法中，从尘埃连续数据获得的高精度物理结构作为最先进的化学模型的独立输入，从而允许我们限制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.