Resolving the physical conditions of concentrated cores in nearby clouds

恒星形成于由致密气体和尘埃组成的小尺度“核心”的分子云中。 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。 虽然在这方面取得了一些进展，但目前的仪器在揭示内核的内部密度、温度和动力学结构方面的能力有限。 这些数据很重要，因为它们提供了我们可以理解核心如何有效地制造恒星的背景，并提供了对磁盘和流出形成的洞察。 在这个建议中，我们描述了一个全面的计划，两个研究生探索核心的内部物理结构，使用新的观测仪器，将很快成为可用。 特别是，我们专注于“集中的核心”，那些相对高的柱密度和小尺寸，可能代表的时代附近的引力核心崩溃的时刻，即，原恒星的形成 这样的核心将很快被发现，从目前的调查亚毫米连续发射横跨几个附近的分子云。 学生们将进行补充项目，每个项目将使用不同的示踪剂恢复浓缩核心的内部物理特性。 特别是，其中一个将用绿色堤望远镜（GBT）和扩展甚大阵（EVLA）观测朝向集中核心的NH 3谱线和射电连续谱发射，而另一个将用詹姆斯·克拉克麦克斯韦望远镜（JCMT）和阿塔卡马大毫米阵（阿尔马）观测朝向相同核心的N2 H+和H2 D+谱线和亚毫米波连续谱发射。

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).