Resolving the physical conditions of concentrated cores in nearby clouds

恒星在分子云中形成，由致密气体和尘埃组成的小尺度“核心”。原则上，气体和尘埃的排放可以用来确定这些核心的物理条件，特别是在附近的云层中。虽然在实现这一目标方面取得了一些进展，但目前的仪器在揭示岩心内部密度、温度和动力结构方面的能力有限。这些数据很重要，因为它们提供了一个背景，使我们能够了解核心形成恒星的效率，并为盘和流出物的形成提供了见解。在本提案中，我们为两位研究生描述了一个全面的计划，利用即将推出的新观测仪器探索岩心的内部物理结构。我们特别关注“集中核心”，即那些柱密度相对较高、尺寸较小的核心，它们可能代表了引力核心坍缩时刻附近的时代，即原恒星的形成。从目前对附近几个分子云的亚毫米连续辐射的调查中，很快就会发现这样的核心。学生将进行互补项目，每个项目将使用不同的示踪剂恢复浓缩岩心的内部物理性质。其中，一个将利用格林班克望远镜（GBT）和扩展超大阵列（EVLA）观测到NH3线和射电连续辐射，另一个将利用詹姆斯·克拉克·麦克斯韦望远镜（JCMT）和阿塔卡马大型毫米波阵列（ALMA）观测到N2H+和H2D+线和亚毫米连续辐射。

Stars form in molecular clouds out of smaller-scale "cores" of dense gas and dust. In principle, emission from gas and dust can be used to determine the physical conditions of such cores, especially in nearby clouds. Though some progress has been made towards this goal, current instruments have been limited in their ability to reveal the internal density, temperature and dynamical structures of cores. Such data are important because they provide the context from which we can understand how efficiently cores make stars, and provide insight into the formation of disks and outflows. In this proposal, we describe a comprehensive plan for two graduate students to explore the interior physical structures of cores, using new observational instrumentation that will become available soon. In particular, we focus on "concentrated cores," those of relatively high column density and small size that likely represent the epoch near the moment of gravitational core collapse, i.e., the formation of the protostar. Such cores will be found soon from current surveys of submillimetre continuum emission across several nearby molecular clouds. The students will undertake complementary projects, where each will recover aspects of the interior physical properties of concentrated cores using different tracers. In particular, one will observe NH3 line and radio continuum emission toward concentrated cores with the Green Bank Telescope (GBT) and the Expanded Very Large Array (EVLA), while the other will observe N2H+ and H2D+ line and submillimetre continuum emission toward the same cores with the James Clerk Maxwell Telescope (JCMT) and the Atacama Large Millimeter Array (ALMA).