A Northern Hemisphere Survey of the Diffuse Interstellar H+

该合同为北半球微弱的星际h - α（6563埃）氢复合线的高通量法布里-珀罗光谱仪提供仪器和支持。这些观测将首次提供漫射星际介质中温暖的电离成分的分布和运动学的详细图像。在许多方面，通过光学h - α线对漫射电离氢的调查将类似于早先通过射电21厘米线对中性氢进行的全天调查。科学回报应该是可观的，因为这种电离气体是星际介质的主要组成部分，但人们对它知之甚少，它的质量大约是中性原子氢的三分之一，占星际能量预算的很大一部分；它似乎也是下银河晕中星际物质的主要状态。因此，这次调查将对我们理解星际介质的组成和结构以及银河盘和晕内电离和加热的主要过程产生重大影响。此外，为了准确解释在无线电、微波、红外、紫外线甚至伽马射线波长上获得的巡天数据，需要对这一分量进行调查。

This award provides instrumentation and support for a northern hemisphere survey of the faint interstellar H-alpha (6563 Angstroms) hydrogen recombination line with a high throughput Fabry-Perot spectrometer. These observations will provide for the first time a detailed picture of the distribution and kinematics of the warm, ionized component of the diffuse interstellar medium. In many respects this survey of the diffuse ionized hydrogen through the optical H-alpha line will be analogous to earlier all- sky surveys of the neutral hydrogen made through the radio 21 cm line. The scientific return should be substantial, since this ionized gas is a major, but poorly understood component of the interstellar medium, which has a mass approximately one-third that of the neutral atomic hydrogen and accounts for a large fraction of the interstellar power budget; it also appears to be the dominant state of interstellar matter in the lower Galactic halo. This survey therefore will have a significant impact on our understanding of the composition and structure of the interstellar medium and the principal processes of ionization and heating within the Galactic disk and halo. Furthermore, a survey of this component is needed for accurate interpretations of sky survey data obtained at radio, microwave, infrared, ultraviolet, and even gamma-ray wavelengths.