Magnetic Fields and Carbon Chemistry in Star Forming Regions

这一提议关注了现代天体物理学中两个及时而重要的问题：1)什么样的恒星和行星形成环境会形成生物学上重要的分子，以及在不同的区域，什么样的化学物质占主导地位？2)磁场如何影响恒星形成分子云的形状和结构，这又如何影响随后恒星和行星的形成？为了解决这些问题，我请求资助两个长期研究项目。1)复杂有机分子（COM）与碳链分子（CCM）在高质量恒星形成（HMSF）区域的研究复杂分子已经在许多不同的空间环境中被发现。尽管人们对COMs的天体生物学重要性给予了很多关注，但ccm在生物学上也很重要，因为即使是像c-C3H2这样的简单环状物质也可能是产生更大生物分子的关键；比如碳水化合物。虽然迄今为止的大多数研究都集中在一些孤立的低质量核心上，但大多数恒星（包括低质量恒星）都是在HMSF区域形成的。已知COMs在HMSF区域的热核中丰富。然而，CCMs被认为在这些地区缺乏。因此，在本项目中，我们将开展一项观测活动，在HMSF地区的样本中检测和绘制各种ccm。对观测数据进行建模将帮助我们了解时间尺度和物理条件（即密度、紫外线场强、温度等），这些对确定HMSF区域的观测丰度很重要，并将其与低质量核的类似观测和理论工作直接进行比较。2)与恒星形成分子云相关的大尺度磁场的三维形态和强度研究。研究表明，磁场在分子云的形成和演化中可能很重要。特别是，有人提出，包裹在云周围的螺旋磁场可以稳定它，防止引力坍缩。然而，这种螺旋场的存在还缺乏观测证实。这主要是因为测量云层磁场强度的传统方法存在一些固有的困难。在过去的几年里，我们创造了一种新的技术来测量分子云中的视线磁场（Blos）。使用这种技术，我们发现Blos是围绕云的一致的螺旋场，但由于数据的限制，我们不能排除其他几何形状。在这个项目中，我们建议改进我们的技术，并在VLA望远镜上开始了一个项目，以更高的灵敏度调查分子云样本。目标是在分子云中产生高灵敏度，高分辨率的三维磁场几何图，误差足够小，我们可以自信地确定磁场几何。

This proposal focusses on two timely and important questions in modern astrophysics: 1) Which star & planet forming environments form biologically important molecules, and what kinds of chemistries dominate in different regions? 2) How do magnetic fields affect the shape and structure of star forming molecular clouds, and how does this influence the subsequent formation of stars and planets? To address these questions, I request funding to support two long-term research projects. 1) A study of Complex Organic Molecules (COM) vs Carbon Chain Molecules (CCM) in High Mass Star Forming (HMSF) regions Complex molecules have been identified in many different environments in space. While much attention has been given to the astrobiological importance of COMs, CCMs are also biologically important because even simple ring species like c-C3H2 may be key to producing larger biomolecules; such as carbohydrates. While most studies to date have focussed on a few isolated, low mass cores, most stars (including low mass stars) form in HMSF regions. COMs are known to be abundant in hot cores in HMSF regions. CCMs, however, are thought to be deficient in these regions. Therefore, in this project we will embark upon an observational campaign to detect and map a variety of CCMs in a sample of HMSF regions. Modeling of the observations will help us understand the time scales and physical conditions (i.e. density, UV field strength, temperature, etc) that are important in setting the observed abundances in HMSF regions and directly compare this to similar observational and theoretical work for low mass cores. 2) A study of the 3D morphology and strength of large-scale magnetic fields associated with star forming molecular clouds. Studies have shown that magnetic fields can be important in the formation and evolution of molecular clouds. In particular, it has been proposed that a helical magnetic field wrapping around a cloud could stabilize it against gravitational collapse. The existence of such helical fields, however, has lacked observational confirmation. This is mainly because the traditional methods to measure magnetic field strengths in clouds have a number of inherent difficulties. Over the past few years we have created a new and novel technique to measure the line-of-sight magnetic field (Blos) in molecular clouds. Using this technique, we found that Blos was consistent helical fields wrapping around the clouds but, due to limitations in the data, we could not rule out other geometries. In this project we propose to refine our technique and have embarked on a project at the VLA telescope to survey a sample of molecular clouds with greater sensitivity. The goal is to produce highly sensitive, high resolution maps of the 3D magnetic field geometry in molecular clouds with small enough errors that we can confidently determine the magnetic field geometry.