Orbital Dynamics in Asymmetric Galaxies -- Exploring the Gravitational Potential

非对称星系中的轨道动力学——探索引力势

• 批准号: 0098419
• 负责人: Linda Sparke
• 金额: $ 18万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098419&HistoricalAwards=false
• 关键词: Orbital; Dynamics; Asymmetric; Galaxies; Exploring

ABSTRACT AST 0098419SparkeMost of the Universe's mass emits no light; we know of its existence only through its gravitational pull on the luminous stars and gas. Within galaxies, this `dark matter' is most influential in the outer parts. This project will study polar ring galaxies. In these, a huge ring of gas, stars and dust encircles a rotating inner disk of stars, much like our own Milky Way -- but the ring stands perpendicular to the central disk. The motions of stars and gas in both the ring and the central galaxy are controlled by gravitational forces, including those of the `dark halo' of non-luminous matter. If the dark halo is roughly spherical, gas in the ring should orbit in circles around the galaxy center, while if the dark stuff lies in a Milky-Way-like disk, the ring will be squashed into an oval by its gravitational force. From observations these motions, the investigators will determine whether the halo is roughly round, or forms a flattened disk. The latter finding would support the idea that the dark material is 'normal' matter (such as burned-out stars), rather than weakly-interacting particles that have not yet been observed on Earth.The investigators also intend to study another gravitational problem: the orbits of stars that experience a gravitational force that is not always the same, but varies with time. An example is that of a star belonging to a small galaxy that follows an elliptical orbit around a much larger galaxy -- our Milky Way has several such satellites. As the satellite swoops in low, the increased gravitational force of the Milky Way can remove stars from its outer regions. The PI has developed a novel method, that of 'invariant loops', that will be used to tackle this problem, and to find which stars will remain with the satellite and which will be stripped from it. It will then be possible to use observations of stars around these small galaxies, now being gathered by the Sloan Digital Sky Survey and other surveys, to measure the gravitational force of the satellite galaxy in comparison to that of the Milky Way. In this way the masses of the satellites can be estimated and their 'dark matter' content calculated. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***

宇宙的大部分物质都不发光，我们只能通过它对发光恒星和气体的引力来知道它的存在。在星系内，这种“暗物质”在外部最有影响力。 该项目将研究极环星系。 在这些星系中，一个巨大的气体、恒星和尘埃环环绕着一个旋转的恒星内部圆盘，就像我们的银河系一样--但是这个环垂直于中心圆盘。 在环和中央星系中，恒星和气体的运动都受到引力的控制，包括不发光物质的“暗晕”。 如果暗晕大致是球形的，环中的气体应该绕着星系中心绕圈运行，而如果暗物质位于一个类似银河系的圆盘中，环将被其引力挤压成椭圆形。 通过观察这些运动，研究人员将确定晕是大致圆形的，还是形成一个扁平的圆盘。 后一个发现支持了暗物质是“正常”物质（如燃尽的恒星）的观点，而不是在地球上尚未观察到的弱相互作用粒子。研究人员还打算研究另一个引力问题：受到引力的恒星的轨道并不总是相同，而是随着时间而变化。 一个例子是，一颗属于小星系的星星沿着椭圆形轨道围绕一个大得多的星系运行--我们的银河系有几颗这样的卫星。 当卫星低空俯冲时，银河系引力的增加可以将恒星从其外部区域移走。 PI已经开发出一种新的方法，即“不变环”，将用于解决这个问题，并找到哪些恒星将留在卫星上，哪些将从卫星上剥离。然后就可以使用这些小星系周围恒星的观测结果，现在正在收集斯隆数字天空调查和其他调查，来测量卫星星系和银河系的引力对比。 通过这种方式，可以估计卫星的质量，并计算它们的“暗物质”含量。该项目的资金由美国国家科学基金会的河外天文宇宙学计划（AST/EXC）提供。