Measurements of Magnetic Field Strengths in the Galaxy

AST0307642特罗兰博士肯塔基大学的托马斯·特罗兰将实施一项观测计划，以确定我们银河系及略高于银河系的磁场强度。利用射频塞曼效应，特罗兰博士和他的合作者将测量扩散中性氢(HI)气体、巨型分子云(GMC)团间介质、分子核以及与大质量恒星形成相关的非常密集的震后区域的场强。这些测量将涵盖广泛的密度范围，它们将有助于回答一些重要的问题。例如，漫射星际介质(ISM)中阿尔夫文克马赫数的范围是多少？扩散气体的两个主要成分之间的场强如何与气体密度成比例关系？高速云(HVC)中的磁场有多强？考虑到最近的理论研究表明磁流体(MHD)湍流是短暂的，静电场是否足够强，足以为GMC提供长期支持？静电场是否足够强，足以为分子核提供支持，以及电场强度如何随分子核内气体密度的变化而变化？磁场在H2O脉泽探测的震后流出区中的作用是什么？这些磁场在脉泽点之间的相关性如何？在许多情况下，这些问题的答案正在浮现，但数据仍然如此稀少，以至于不可能得出有充分依据的结论。为了执行这个项目，特罗兰博士将利用现有的射电天文仪器和新的射电天文仪器。最著名的新仪器是绿岸望远镜(GBT)。这个望远镜专门为超低副瓣响应而设计，应该会对磁场的塞曼效应研究产生深远的影响。特罗兰博士还将使用阿雷西博望远镜，可能还会使用IRAM 30米望远镜作为该项目的一部分。新的仪器能力与日益增长的MHD数值模拟理论能力相辅相成。在接下来的几年里，在观测和理论方面的进展可能会大大增加我们对星际磁现象的理解。这项研究计划将涉及肯塔基大学的研究生教育。它还将涉及与东肯塔基大学的一位新的地区同事(前研究生)Anuj Sarma博士的合作。EKU是一所本科院校，致力于将研究经验带给学生。Sarma参与研究计划不仅对科学产出很重要，还将帮助他在自己的机构建立一个研究计划。***

AST 0307642TrolandDr. Thomas Troland, at the University of Kentucky, will carry out an observational program to determine magnetic field strengths in our Galaxy and slightly beyond. Using the radio frequency Zeeman effect, Dr. Troland and collaborators will measure field strengths in the diffuse neutral hydrogen (HI) gas, in the interclump medium of giant molecular clouds (GMCs), in molecular cores, and in very dense post-shock regions associated with massive star formation. These measurements will cover a wide density range, and they will help answer a number of important questions. For example, what is the range of Alfvenic Mach numbers in the diffuse interstellar medium (ISM)? How do field strengths scale with gas density among the two main components of the diffuse gas? How strong is the magnetic field in high velocity clouds (HVCs)? Are static fields strong enough to provide long term support to GMCs given recent theoretical studies suggesting magneto-hydrodynamic (MHD) turbulence is short-lived? Are static fields strong enough to provide support for molecular cores, and how does the field strength scale with gas density within them? What is the role of magnetic fields in the post-shock outflow regions probed by H2O masers, and how coherent are these fields among maser spots? In many cases, answers to these questions are emerging, but data are still so sparse that it is impossible to draw well-founded conclusions.To carry out this program, Dr. Troland will make use of established radio astronomy instruments as well as new ones. The most prominent new instrument is the Green Bank Telescope (GBT). Expressly designed for ultra-low sidelobe response, this telescope should have a profound effect upon Zeeman effect studies of the magnetic field. Dr. Troland will also use the Arecibo telescope and possibly the IRAM 30m telescope as a part of this program. New instrumental capabilities are complemented by growing theoretical capabilities for numerical simulation of MHD. Advances on both the observational and theoretical fronts in the next few years are likely to significantly increase our understanding of interstellar magnetic phenomena.This research program will involve graduate education at the University of Kentucky. It will also involve collaboration with a new regional colleague (and former graduate student) Dr. Anuj Sarma of Eastern Kentucky University. EKU is an undergraduate institution with an interest in bringing research experiences to its students. Sarma's participation in the research program will not only be important for the science output, it will also help him establish a research program at his own institution. ***