The Milky Way Galaxy at 21-cm

AST 0307603 Dickey银河系平面上的大多数恒星、尘埃和气体都集中在南部天空中一个只有几百平方度的窄带中。天文学家对这一区域进行了深入的研究，特别是那些研究无线电、红外线和X射线辐射的天文学家，这些辐射不会被星际介质所掩盖。这个项目由明尼苏达大学的John Dickey博士领导，是对这个区域的光谱调查，银河系的第一和第四象限，使用中性原子氢（HI）的21厘米线。该项目是成功的南银河平面调查（SGPS）的延伸，该调查是由明尼苏达大学领导的美国和澳大利亚天文学家之间的合作。该调查使用澳大利亚望远镜国家设施的两个天文台（帕克斯和紧凑阵列），结合单盘和干涉仪数据来获得高角分辨率，同时保持对大尺度亮度分布的灵敏度。这代表了一个数量级的改善，分辨率比以前的调查南银河系。现在的目标是完成整个银河系内部的区域，将SGPS与北部的加拿大银河系平面调查结合起来，制作整个银河系盘的单一无缝地图集。这将是来自几个国家天文台的数据的组合，包括美国国家射电天文台的绿色银行望远镜和超大阵列。 这些观测揭示了星际介质（ISM）原子相的天体物理学。吸收光谱和发射光谱一起确定了整个银河系中性氢的温度和丰度，作为半径和中平面以上高度的函数。银河系盘中有大量的星际氢原子云;巡天数据提供了一个巨大的云、片和其他ISM特征的图集。由于原子介质是如此广泛，它跟踪最大的结构，如超级壳和烟囱，从磁盘到达晕排放超新星注入的热气。ISM中的暖原子阶段和冷原子阶段是银河系演化周期中的关键阶段;这项调查显示了物质如何从一代恒星到下一代恒星通过这些阶段。 该项目为研究生和本科生提供教育机会。它将成为两个或更多博士学位的主题。论文，和几个高级荣誉论文。在公共宣传方面，调查项目将成为一个录像记录片以及许多公开演讲的主题。本次调查的数据将免费分发给所有人。SGPS地图已经提供给世界各地的十几位天文学家，以支持他们自己的研究。21厘米的线立方体提供了在其他波长下看到的物体的背景;这次调查的地图显示了HII区域周围区域的气体密度和速度场，分子云，超新星遗迹和各种银河系现象。

AST 0307603DickeyMost of the stars, dust, and gas in the plane of the Milky Way are concentrated in a narrow band of only a few hundred square degrees across the southern sky. This area is intensely studied by astronomers, particularly those working with radio, infrared, and X-ray radiation that are not obscured by the interstellar medium. This project, led by Dr. John Dickey at the University of Minnesota, is a spectroscopic survey of this area, the first and fourth quadrants of the Galaxy, using the 21-cm line of neutral atomic hydrogen (HI). This project is an extension of the successful Southern Galactic Plane Survey (SGPS), a collaboration among astronomers in the United States and Australia led by the University of Minnesota. That survey uses the two observatories of the Australia Telescope National Facility (Parkes and the Compact Array), combining the single dish and interferometer data to obtain high angular resolution while preserving the sensitivity to the largescale brightness distribution. This represents an order of magnitude improvement in resolution over previous surveys of the Southern Milky Way. Now the goal is to complete the entire area of the inner Galaxy, to join the SGPS with the Canadian Galactic Plane Survey in the north, to produce a single, seamless atlas of the entire Milky Way disk. This will be a combination of data from observatories in several countries, including the U.S. National Radio Astronomy Observatory's Green Bank Telescope and Very Large Array. The astrophysics of the atomic phases of the interstellar medium (ISM) is revealed by these observations. Absorption and emission spectra together specify the temperature and abundance of the neutral hydrogen all over the Galaxy, as a function of radius and height above the mid-plane. Interstellar clouds of atomic hydrogen are abundant in the Galactic disk; the survey data provide a huge atlas of clouds, sheets, and other ISM features. Because the atomic medium is so widespread,it traces the largest structures, such as supershells and chimneys that reach from the disk up into the halo to vent hot gas injected by supernovae. The warm and cool atomic phases in the ISM are critical stages in the cycle of Galactic evolution; this survey shows how matter moves through these stages from one generation of stars to the next. This project provides educational opportunities for graduate and undergraduate students. It will be the subject for two or more Ph.D. theses, and several senior honors theses. In the area of public outreach, the survey project will be the subject of a video documentary, as well as many public talks. The data from this survey will be distributed freely to all. The SGPS maps have already been given to more than a dozen astronomers all over the world to support their own research. The 21-cm line cubes provide the context for objects seen at other wavelengths; maps from this survey show the gas density and velocity fields in the area surrounding HII regions, molecular clouds, supernova remnants, and all kinds of Galactic phenomena.***