Galactic Warps and Polar Rings

人们普遍认为，有9320403个火花星系有看不见的“暗”晕，其中包含了该星系的大部分质量。光晕比发光物质的范围更广，其质量分布最好通过研究恒星和气体的最外层轨道来探测。螺旋星系中翘曲的圆盘和围绕着SO星系的极环的模型表明，这些结构可以被理解为大质量晕势中的自引力结构。翘曲或极环的预期形状，以及这些结构中轨道的速度，取决于看不见的光晕内质量的分布情况：中心集中度，垂直于圆盘平面的扁平度，以及它是否显著地三轴。将为理论建模和观测提供支持。有关翘曲的理论工作将解决星系凸起的影响，具有不同方位依赖关系的翘曲，以及由于与光晕相互作用而最终产生的翘曲衰减。还将对翘曲系统进行光学和HI观测。极环的动力学建模将集中在三轴性的影响上，并为特定的观测系统建立详细的模型以建立参数；观测计划包括环的高分辨率HI映射、射电测量、光学成像和光谱分析

9320403 Sparke Galaxies are widely believed to have unseen 'dark' halos containing much of the mass of the system. The halo is more extended than the luminous material, and its mass distribution is best probed by studying the outermost orbits of stars and gas. Models for warped disks in spiral galaxies, and for polar rings around SO galaxies, show that these can be understood as self- gravitating structures in the potential of the massive halo. The form expected for the warp or the polar ring, and velocities of orbits within these structures, depend on how mass is distributed within the unseen halo: on the central concentration, on the flattening normal to the disk plane, on whether it is significantly triaxial. Support will be provided both for theoretical modeling and observations. Theoretical work on warps will address the effect of a galactic bulge, warps with different azimuthal dependences, and the eventual damping of warps due to interaction with the halo. Optical and HI observations of warped systems will also be made. Dynamical modeling of polar rings will concentrate on the effect of triaxiality, and on detailed models for particular observed systems to establish parameters; the observational program includes high-resolution HI mapping of the rings, radio surveys, and optical imaging and spectroscopy