Diffuse Ionized Gas in Galactic Halos: Multiwavelength Studies of the Milky Way and Magellanic System with WHAM-South

银河晕中的弥散电离气体：利用 WHAM-South 对银河系和麦哲伦系统进行多波长研究

• 批准号: 1108911
• 负责人: Lawrence Haffner
• 金额: $ 224.35万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1108911&HistoricalAwards=false
• 关键词: Diffuse; Ionized; Gas; Galactic; Halos

This renewal project is for the completion of the first comprehensive view of the distribution and kinematics of the Milky Way's ionized gas regions in the local universe using the Wisconsin H-Alpha Mapper (WHAM), a remotely controlled Fabry-Perot astronomical facility. WHAM collects high-resolution optical emission-line spectra from faint, diffuse sources, and its focused design is sensitive to detect emission nearly a 100 million times fainter than the Orion Nebula. With the instrument's new location on Cerro Tololo in Chile, the investigators can target regions to determine the distribution and physical properties of diffuse ionized gas over the southern sky of the Milky Way. The investigators completed the first systematic spectral survey of the Milky Way in the Balmer-alpha (H-alpha) emission line of hydrogen. This all sky survey provides a sensitive view of ionized gas, and found a mix of bright, discrete H II regions intertwined with large filaments, bubbles, and shells and revealed a faint, pervasive background detected over the whole sky known as the warm ionized medium (WIM).WHAM's new view includes one of the brightest, extended regions of emission above star-forming regions in the inner Galaxy as well as one of the largest diffuse H II regions in our sky. Spectra are used to study the distribution of ionization and temperature of the gas within locally ionized regions and across large regions of the Milky Way. The velocity of emitting regions and the relationship of ionized gas to nearby hot stars and neutral gas in large-scale structures can be influenced by past and present generation of relatively short-lived massive stars. The study of complex regions provides insights to energy transport processes in the Galactic disk and halo and traces active star formation in the Galactic spiral arms, which is challenging to map accurately.WHAM's kinematic resolution and multi-wavelength capability can isolate specific large-scale emission features, which will provide a better understanding how these features depend on environment, metallicity, and local star formation rate. This study will complete several comprehensive, multiline studies of large-scale emission in the Galaxy. The strengths of optical emission from nitrogen, sulfur, oxygen, and helium relative to that of hydrogen depend on the composition, temperature, heating, and ionization of the gas. The derived properties of the warm ionized medium (WIM) in the inner Galaxy will be compared to those in the outer Galaxy. Another goal is to study the ionized component of the extended gaseous structures such as the Magellanic Stream, Bridge, and Leading Arm of the Magellanic System, where elemental abundances, dust content, and radiation fields differ significantly from those in our Galaxy. This helps to understand how such ionized regions can be maintained so far from active star formation and whether the ionized component contains a significant amount of mass that not yet been detected.The WHAM project provides excellent opportunities for undergraduate and graduate students to participate and interact with a research-grade astronomical observatory. It contributes to technological advances in remote observing techniques to improve the quality and efficiency of data collection. The high-quality datasets will be of use by the entire astronomical community. The observations provide essential direction for new, large-scale MHD simulations of a multiphase interstellar medium where ISM matter and energy are transferred to and from stars. WHAM contributes to the fields of aeronomy, solar system astronomy, extragalactic astronomy, and cosmology. Its deep sensitivity and velocity resolution enable studies of the Earth's atmosphere, comets, and zodiacal dust. The full characterization of the faint but pervasive ionized gas in the Galaxy needs to be understood for the analysis of extragalactic and cosmic backgrounds.

这一更新项目是为了利用威斯康星州H-阿尔法成像仪（WHAM）这一遥控法布里-珀罗天文学设施完成对银河系电离气体区域在本宇宙中的分布和运动学的第一次全面观测。WHAM从微弱的漫射源收集高分辨率的光学发射线光谱，其聚焦设计对检测比猎户座星云微弱近1亿倍的发射非常敏感。随着该仪器在智利Cerro Tololo的新位置，研究人员可以瞄准区域，以确定银河系南部天空弥漫电离气体的分布和物理特性。研究人员完成了对银河系在氢的巴耳默-阿尔法（H-阿尔法）发射线的首次系统光谱调查。这次全天空巡天提供了电离气体的敏感视图，并发现了一个明亮的，离散的H II区域与大细丝，气泡和外壳交织在一起的混合物，并揭示了在整个天空中检测到的一个微弱的，普遍的背景，称为温暖的电离介质（WIM）。WHAM的新视图包括最亮的，在银河系内部的恒星形成区域上方的辐射扩展区域，以及我们天空中最大的弥漫H II区域之一。光谱被用来研究局部电离区域和银河系大区域内气体的电离和温度分布。在大尺度结构中，发射区的速度以及电离气体与附近热恒星和中性气体的关系可能会受到过去和现在相对短寿命的大质量恒星的影响。对复杂区域的研究有助于深入了解银河系盘和晕中的能量传输过程，并追踪银河系旋臂中活跃的星星形成过程，这对精确绘制具有挑战性。WHAM的运动学分辨率和多波长能力可以分离出特定的大尺度发射特征，这将有助于更好地了解这些特征如何依赖于环境，金属丰度和局部星星形成率。这项研究将完成对银河系大规模辐射的几项全面、多线研究。氮、硫、氧和氦相对于氢的光发射强度取决于气体的组成、温度、加热和电离。在银河系内部的温暖的电离介质（WIM）的派生属性将进行比较，在外部星系。另一个目标是研究扩展气体结构的电离成分，如麦哲伦流，桥和麦哲伦系统的主导臂，其中元素丰度，尘埃含量和辐射场与我们的银河系有很大不同。这有助于了解这些电离区域如何在远离活跃的星星形成的情况下得以维持，以及电离成分是否包含大量尚未被探测到的质量。WHAM项目为本科生和研究生提供了参与研究级天文观测台并与之互动的绝佳机会。它有助于远程观测技术的技术进步，以提高数据收集的质量和效率。高质量的数据集将被整个天文学界使用。 这些观测结果为新的、大规模的多相星际介质MHD模拟提供了重要的方向，在该多相星际介质中，ISM物质和能量被转移到恒星和从恒星转移。WHAM在高层大气物理学、太阳系天文学、河外天文学和宇宙学领域做出了贡献。它的深度灵敏度和速度分辨率使研究地球的大气，彗星和黄道尘。银河系中微弱但普遍存在的电离气体的完整特征需要理解，以便分析河外和宇宙背景。