Comparing Theory with Observation Using Chemical Probes of Turbulent Molecular Clouds

我们对恒星形成的星际分子气云的了解主要依赖于对CO、水和氨等痕量分子的谱线的观察。最近这些分子云的模型表明，它们是寿命在1000万年以下的动态物体，而云中的核心通常代表动态坍塌的物体。然而，这些模型产生了密度、温度和速度等物理变量，这些变量很难直接与观测到的谱线强度图进行比较。该项目通过在磁流体动力学湍流的三维数值模拟中直接跟踪分子物种的形成和演化，消除了阻碍这种比较的一个困难，包括自引力的影响。还将进行近似，以模拟紫外线辐射对化学的影响。通过比较化学丰度的测量，以及用迭代方法模拟通过湍流气体的线传输，将直接与观测结果进行比较。这些模拟将被用来研究一系列问题；例如，当前对分子云的观测是否可以用来限制湍流的性质，以及模拟核心的化学成分是否与观察到的真实核心的组成相一致。这个项目中计算的模型将作为美国自然历史博物馆数字收藏的一部分，以适合于模拟各种不同仪器的观测的形式免费提供给观察者。这项研究还将被纳入对媒体、在职教师和普通公众以及哥伦比亚大学课堂上正在进行的研究报告中。这项研究将在与英国同事的国际合作中进行。

AST 0307793GloverOur understanding of the interstellar clouds of molecular gas where stars form depends primarily on observations of spectral lines from trace molecules such as CO, water, and ammonia. Recent models of these molecular clouds have suggested that they are dynamical objects with lifetimes under 10 million years, and that cores within the clouds usually represent dynamically collapsing objects. However, the models yield physical variables such as density, temperature, and velocity, whichare difficult to compare directly to observed maps of line intensity. This project removes one difficulty standing in the way of that comparison by directly following the formation and evolution of molecular species in three-dimensional numerical simulations of magnetohydrodynamical turbulence, including the effects of self-gravity. Approximations will also be made to model the effects of UV radiation on the chemistry. Direct comparisons to the observations will be made by comparing measurements of chemical abundances, and by modeling line transfer through the turbulent gas with an iterative method. The simulations will be used to study a number of problems; for instance, whether current observations of molecular clouds can be used to constrain the nature of the turbulence, and whether the chemical composition of simulated cores is compatible with the observed composition of real cores.The models computed in this project will be made freely available to observers in a form suitable for simulating observations from a wide variety of different instruments, as part of the digital collection of the American Museum of Natural History. This research will also be incorporated into ongoing presentations of research to the media, in-service teachers, and the general public, as well as classes at Columbia University. This research will be done in an international collaboration withcolleagues in the United Kingdom.***