Comparing Theory with Observation Using Chemical Probes of Turbulent Molecular Clouds

我们对恒星形成的星际分子气体云的理解主要依赖于对微量分子如一氧化碳、水和氨的光谱线的观测。这些分子云的最新模型表明，它们是动态的物体，寿命在1000万年以下，而云内的核心通常代表动态坍缩的物体。然而，这些模型产生了诸如密度、温度和速度等物理变量，这些变量很难直接与观测到的线强度图进行比较。这个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，包括自重力的影响，消除了阻碍这种比较的一个困难。还将进行近似模拟，以模拟紫外线辐射对化学的影响。将通过比较化学丰度的测量值和用迭代方法模拟湍流气体中的线传递来与观测结果进行直接比较。模拟将用于研究一些问题；例如，目前对分子云的观测是否可以用来约束湍流的性质，以及模拟核的化学成分是否与观测到的真实核的成分相一致。在这个项目中计算出的模型将作为美国自然历史博物馆数字收藏的一部分，以一种适合于模拟各种不同仪器观测结果的形式免费提供给观察者。这项研究也将被纳入正在进行的对媒体、在职教师、公众以及哥伦比亚大学课堂的研究报告中。这项研究将与英国的同事进行国际合作

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.***