Cool Atomic Clouds in Spiral Galaxies

螺旋星系中的冷原子云

• 批准号: 8722990
• 负责人: John Dickey
• 金额: $ 12.04万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-08-15 至 1993-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8722990&HistoricalAwards=false
• 关键词: Cool; Atomic; Clouds; Spiral; Galaxies

The research will involve a study of the cool atomic phase of the interstellar medium in the disks of nearby spiral galaxies. The purpose of the research is to measure the relative fractions of warm and cool interstellar atomic hydrogen (HI). This fraction is a sensitive function of the heating process and the interstellar pressure. The second objective is to measure the cloud size spectrum in the mass range one hundred to several thousand solar masses. The observations will show whether the abundance of these of these atomic clouds increases with decreasing galactic radius, as do the molecular clouds in most spirals, or whether the atomic clouds are depopulated where the molecular clouds are most abundant. The third objective is to measure the cross-sections of spiral galaxies for 21 cm wavelength absorption. This will provide a better understanding of the origin of HI absorption lines at high redshifts. The observing technique will be to measure 21 cm absorption spectra through the disks of 50 nearby spiral galaxies. All Shapley- Ames catalog of galaxies (blue magnitude less than 12) with suitable background sources will be observed, and very nearby galaxies (designated M31, M33, and M81) will be studied along several lines of sight. The recent expansion of the Very large Array (VLA) on-line data reduction system makes this feasible for the first time. The basic purpose of this research will be to understand the abundance and distribution of cool interstellar clouds in spiral galaxies and to determine whether molecular and atomic clouds are a single population or two distinct species.

这项研究将涉及对冷原子相的研究， 附近螺旋星系盘中的星际介质。 的 研究的目的是测量 温暖和寒冷的星际原子氢（HI）。 该馏分 是加热过程的敏感函数， 星际压力 第二个目标是测量 质量范围在100到几个的云大小谱 千个太阳质量 观察结果将显示， 这些原子云的丰度随着 星系半径逐渐减小，大多数星系中的分子云也是如此。 螺旋，或者原子云是否在 分子云最丰富。 第三个目标是 测量螺旋星系的21厘米横截面 波长吸收 这将提供一个更好的理解 的起源HI吸收线在高红移。 的 观测技术将是测量21厘米吸收光谱 穿过附近50个螺旋星系的圆盘 所有沙普利- 星系的艾姆斯星表（蓝色星等小于12）， 将观察到合适的背景源，并且非常接近 星系（命名为M31，M33和M81）将被沿着研究 几条视线。 最近扩大的超大型 阵列（VLA）在线数据简化系统使这一点成为可能， 第一次 本研究的基本目的是 了解冷星际物质的丰度和分布 螺旋星系中的云，并确定是否分子和 原子云是一个单一的群体或两个不同的物种。