Continued Exploration of the Warm Ionized Medium using the Wisconsin H-Alpha Mapper

AST 0204973解释星际物质和过程的准确知识对于理解恒星出生和死亡的周期以及星系的演化至关重要。威斯康星州的H-阿尔法绘图仪（WHAM），一个远程控制的法布里-珀罗设施，致力于微弱的弥漫星际发射线的检测和研究，已经打开了一个新的窗口，星际介质，使之有可能第一次探索气体的温暖电离相尽可能多或更多的精度和细节作为其他主要阶段的介质已探索。这些光学发射线研究提供了关于星际介质的性质以及银河系盘和晕内电离和加热的主要来源的独特的新信息，这些信息无法通过其他波长的其他技术获得。使用WHAM设备，威斯康星州大学的罗纳德雷诺兹博士和他的同事们，将对电离气体内电离和激发条件的变化进行全面研究，并探索辐射场的强度和光谱。他们最近完成的WHAM北方巡天首次全面描绘了这种气体在天空中的分布和运动学，从而为这项调查提供了基本基础。整套调查数据已向社会公布，并可通过网站http://www.astro.wisc.edu/wham/查阅。 在该计划的第二阶段，研究人员将观察较暗的诊断发射线，以探索调查发现的新发射特征的性质，并研究星际介质的这种广泛的低密度相与热恒星附近明亮的经典H II区域之间的温度和电离状态的惊人差异。 通过对氧、氮、硫和氦的微弱发射线的观测，他们将研究弥散发射气体的物理条件，微弱的WHAM“点源”，从银河系中平面达到1000 pc或更多的电离气体的巨大细丝和环，以及电离气体与介质中温暖的中性氢相的关系。通过将这些观测结果与经典O星星H II区以及与高纬度热白色矮星、B星和超新星遗迹相关的电离气体扩展区的观测结果进行比较，他们将研究银河系内这些已知的电离源与介质的温暖电离相之间的关系。对中高速云的观测将用于追踪从银河系中平面到银河系晕的电离气体和辐射场的变化情况，而对H β/H α的观测将提供关于星际尘埃沿着这些光学线研究的视线的影响的信息。在该计划的第一阶段，WHAM对这些和其他微弱发射线进行观测的能力得到了验证。第二阶段的多样化观测计划充分利用了这一强大而独特的设施，并将在我们对银河系盘和晕内星际物质和过程的理解方面取得实质性进展。***

AST 0204973ReynoldsAn accurate knowledge of interstellar matter and processes is crucial to understanding the cycle of stellar birth and death and the evolution of galaxies. The Wisconsin H-Alpha Mapper (WHAM), a remotely controlled Fabry-Perot facility dedicated to the detection and study of faint diffuse interstellar emission lines, has opened a new window to the interstellar medium by making it possible for the first time to explore the warm ionized phase of the gas with as much or moreaccuracy and detail as the other principal phases of the medium have been explored. These opticalemission line studies provide unique new information about the nature of the interstellar mediumand the principal sources of ionization and heating within the disk and halo of the Galaxy,information that cannot be obtained through other techniques at other wavelengths.Using the WHAM facility, Dr. Ronald Reynolds and his colleagues, at the University of Wisconsin, will carry out a comprehensive study of the variations in ionization and excitation conditions within the ionized gas and explore the strength and spectrum of the radiation field. Their recently completed WHAM Northern Sky Survey has given the first comprehensive picture of the distribution and kinematics of this gas over the sky and thus provides the basic foundation for this investigation. The complete set of survey data has been released to the community and is available through the website: http://www.astro.wisc.edu/wham/. In this second phase of the program the investigators will observe fainter diagnostic emission lines to explore the nature of the new emission features discovered by the survey and to study the surprising differences in temperature and ionization state between this widespread, low-density phase of the interstellar medium and the bright, classical H II regions near hot stars. From observations of faint emission lines of oxygen, nitrogen, sulfur, and helium, they will investigate the physical conditions of the diffusely emitting gas, the faint WHAM "point sources", the enormous filaments and loops of ionized gas that reach 1000 pc or more from the Galactic midplane, and the relationship of the ionized gas to the warm neutral hydrogen phase of the medium. By comparing these observations with those toward classical O star H II regions and extended regions of ionized gas associated with high latitude hot white dwarf stars, B stars, and supernova remnants, they will study the relationship between these known sources of ionization within the Galaxy and the warm ionized phase of the medium. Observations of the intermediate and high velocity clouds will be used to trace the changing conditions in the ionized gas and radiation field from the Galactic midplane to the Galactic halo, while observations of H Beta/H Alpha will provide information about the influence of interstellar dust along the lines of sight of these optical line studies. The ability of WHAM to carry out the observations of these and other faint emission lines was verified during the first phase of this program. The diverse observational program in this second phase takes full advantage of this powerful, unique facility and will produce a substantial advancement in our understanding of interstellar matter and processes within the disk and halo of the Milky Way. ***