Resolving the physical conditions of concentrated cores in nearby clouds

恒星是由较小尺度的致密气体和尘埃组成的“核心”分子云中形成的。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。尽管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、温度和动力学结构方面的能力一直受到限制。这样的数据很重要，因为它们提供了一个背景，我们可以从中了解地核如何有效地形成恒星，并提供对圆盘形成和外流的洞察。在这项提议中，我们描述了一项全面的计划，让两名研究生利用即将推出的新的观测仪器来探索岩心的内部物理结构。特别是，我们关注的是“集中核心”，它们具有相对较高的柱密度和较小的尺寸，可能代表了引力核心塌缩时刻附近的纪元，即原恒星的形成。从目前对附近几个分子云的亚毫米级连续辐射的调查中，很快就会发现这样的核心。学生们将进行互补的项目，每个项目都将使用不同的示踪剂恢复浓缩岩芯的内部物理性质的各个方面。特别是，一个将用绿岸望远镜(GBT)和扩展的甚大阵列(EVLA)观测到向集中核心的NH3线和射电连续谱发射，而另一个将用詹姆斯·克莱克·麦克斯韦望远镜(JCMT)和阿塔卡马大毫米阵列(ALMA)观测到向相同核心的N2H+和H2D+线和亚毫米连续谱发射。

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).