Hypercompact HII Regions: A New Stage of O-star Evolution?

超紧凑 HII 区域：O-star 演化的新阶段？

• 批准号: 0303689
• 负责人: Edward Churchwell
• 金额: --
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2008-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0303689&HistoricalAwards=false
• 关键词: Hypercompact; HII; Regions; New; Stage

AST 0303689PI ChurchwellRecent radio observations of massive star formation regions have discovered what appears to be a new class of very compact regions of ionized hydrogen (HII) gas that have been dubbed "hypercompact HII" regions. They have several common properties that distinguish them from ultracompact HII regions and other thermal radio sources. For example they have electron densities ~100 times larger and diameters ~10 times smaller than typical ultracompact HII regions. In addition, they appear to occur in pairs or multiple systems and are located in massive star formation regions. The Principle Investigator speculates that hypercompact regions may represent the transition from the rapid accretion phase of massive protostars in hot molecular cores to the stage where accretion has terminated and an easily detectable ionized hydrogen region has been formed. In this project the PI is characterizing the properties of these hypercompact regions to determine their niche in the early evolution of massive protostars by increasing the sample size, measuring their properties, and also determining the apparent binary frequency and projected separations from high resolution Very Large Array radio continuum images. From new data plus models, the PI is obtaining the structure (morphology, range of diameters), physical properties (velocity structure and distributions of electron density and temperature), and state of evolution of hypercompact regions and hence developing a deeper understanding of massive star formation.Broader Impacts: This project is the PhD thesis topic of a member of an under-represented group in science. Some undergraduates receive their first experience with basic research from first-hand observing experience and data reduction and analysis methods by working on this project. Numerous popular talks are given each year to school groups and service groups. Benefits to society are a generally better understanding of how science works and specifically how stars are made.

AST 0303689 PI Churchwell最近对大质量星星形成区域的射电观测发现了一类新的非常致密的电离氢（HII）气体区域，被称为“超致密HII”区域。它们有几个共同的性质，使它们与超压缩的HII区和其他热射电源区分开来。 例如，它们的电子密度比典型的超紧凑HII区大100倍，直径小10倍。此外，它们似乎成对或多系统出现，并位于大质量星星形成区。首席研究员推测，超致密区域可能代表了从热分子核心中大质量原恒星的快速吸积阶段到吸积终止阶段的过渡，并且已经形成了一个容易检测的电离氢区域。在这个项目中，PI正在表征这些超致密区域的特性，以通过增加样本大小，测量它们的特性，并确定高分辨率甚大阵列无线电连续图像的表观二进制频率和投影分离来确定它们在大质量原恒星早期演化中的位置。 通过新的数据和模型，PI获得了超致密区的结构（形态、直径范围）、物理性质（速度结构、电子密度和温度分布）和演化状态，从而对大质量星星的形成有了更深入的了解。更广泛的影响：本项目是科学界代表性不足的一个小组成员的博士论文课题。一些本科生通过参与该项目，从第一手的观察经验和数据整理与分析方法中获得了基础研究的第一次经验。每年为学校团体和服务团体举办许多受欢迎的讲座。对社会的好处是更好地理解科学是如何工作的，特别是恒星是如何形成的。