Twenty-one Centimeter Hydrogen Line Studies of Galaxy Evolution

星系演化的二十一厘米氢线研究

• 批准号: 8806737
• 负责人: Franklin Briggs
• 金额: $ 1.87万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-09-01 至 1990-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8806737&HistoricalAwards=false
• 关键词: Twenty; Centimeter; Hydrogen; Line; Studies

Nearby galaxies which have an unusually large amount of neutral hydrogen gas can be studied by radio astronomical techniques. The objectives of the observations will be to define the gaseous structures of large, gas-rich galaxies and to see if there are dynamical processes at work now that might have been important in the past. A collaborative program that uses the new receiving systems at the Westerbork (The Netherlands) Synthesis Radio Telescope (WSRT) will be initiated to study the highly redshifted 21 cm wavelength absorption line of hydrogen gas. The instrument is uniquely suited to this type of experiment. The optical survey work on the galaxies which is already in progress will provide candidates for study at radio wavelengths. It is important to emphasize that radio astronomy techniques complement the optical data by providing: (1) Very Long Baseline Interferometric (VLBI) measurements of the spatial extent of the absorbing gas, (2) the neutral hydrogen gas (HI) temperature estimates, and (3) details of the kinematics in the high column density clouds at the heart of the absorption system. This program will be a collaborative effort with an astronomer from the University of Pittsburgh and Netherland astronomers. VLBI spectral line experiments will be carried out to compete with the WSRT. The galaxy system in PKS 0458-02 (redshift z = 2.04) is well-suited to more detailed study. There is radio structure in the background source on a wide range of scales, and the absorption itself is very strong. The precision of the spectral line VLBI observations of this system will be improved and intermediate-length baseline experiments will be attempted, which should detect the structure in the absorber on typical galactic scales. A four-station VLBI experiment including WSRT, Arecibo, Green Bank, and Jodrell Bank would be very useful since the WSRT-Jodrell Bank baseline would be short enough to define the absorption in front of the large (about 2 arcsecond) structure. The intercontinental baselines would detect the fine structure in the absorber against the more compact components. Both Arecibo and Green Bank are already equipped with receivers. Jodrell Bank is planning to build a low noise preamplifier in order to include the 250-foot telescope in the experiment. Since receiving systems have improved by a factor of about 4 in sensitivity since the previous experiment was performed, the VLBI observations of the lower redshift systems (z = 0.69) in the spectrum of 3C286 will be repeated. The inclusion of WSRT and Jodrell Bank in this experiment would be of great interest since the background radio source in 3C286, like PKS 0458-020, has structure on a wide range of scales. The results of the project should improve our understanding of the structure and evolution of galaxies.

可以通过射电天文技术研究附近的星系，具有异常大量的中性氢气。 观察的目标将是定义大型气体富含气的星系的气态结构，并查看过去是否有动态过程在过去可能很重要。 使用Westerbork（荷兰）合成射电望远镜（WSRT）使用新接收系统的协作计划将启动研究高度红移的21 cm波长吸收系的氢气。 该仪器非常适合这种实验。 关于已经进行的星系的光学调查工作将为无线电波长提供研究。 重要的是要强调，通过提供的射电天文学技术补充了光学数据：（1）对吸收气体的空间范围的非常长的基线干涉测量（VLBI）测量，（2）中性氢气（HI）温度估算值，以及（3）高柱密度云中Kinematics的细节在高柱密度云中的详细信息。 该计划将与匹兹堡大学和荷兰天文学家的天文学家进行合作。 VLBI光谱线实验将进行与WSRT竞争。 PKS 0458-02中的星系系统（红移Z = 2.04）非常适合更详细的研究。 背景源中的无线电结构在广泛的尺度上，吸收本身非常强。 该系统的光谱线VLBI观测值的精度将得到改善，并将尝试中等长度的基线实验，该实验应在典型的银河尺度上检测到吸收剂中的结构。 一个四站VLBI实验，包括WSRT，Arecibo，Green Bank和Jodrell Bank非常有用，因为WSRT-JODRELL BANK基线的基线将足够短，可以定义大型（大约2个Arcsect）结构的吸收。 洲际基线将检测吸收器中的细胞结构，以针对更紧凑的成分。 Arecibo和Green Bank都已经配备了接收器。 乔德雷尔银行（Jodrell Bank）计划建立一个低噪声前置放大器，以便在实验中包括250英尺的望远镜。 由于自上一项实验以来，接收系统的灵敏度提高了约4倍，因此将重复3C286的较低红移系统（z = 0.69）的VLBI观察结果。 在该实验中包含WSRT和Jodrell银行将引起人们的极大关注，因为3C286的背景无线电源（如PKS 0458-020）具有广泛的尺度。 该项目的结果应提高我们对星系结构和演变的理解。