Measuring Radially Varying Pattern Speeds in Spiral Galaxies

兰德博士和研究生莎伦·梅特将采用一种新方法来测量盘状星系围绕星系中心旋转的螺旋形和条形图案的速度。这些模式在大多数盘状星系中都有发现，包括我们的银河系。经典的螺旋结构理论假设，一个不稳定的恒星盘会发展出一套生长模式，每一种模式都有固定的速度。在星系盘的引力n体模拟中，已经看到了具有多种模式速度的结构，解释为耦合模式；一般来说，在靠近中心的地方，速度更快的模式占主导地位。兰德博士和他的合作者迈克尔·梅里菲尔德（Michael Merrifield）开发了“改进的Tremaine-Weinberg”方法来测试观察到的螺旋星系是否也有多种模式速度。该方法将应用于7个附近的螺旋星系，它们的速度场已经在CO和中性氢气中得到了很好的映射。这种方法将直接测量模式速度来测试螺旋结构形成的理论模型，并确定螺旋是否随着时间的推移而缠绕。新墨西哥大学既是一所研究型大学，也是一所为西班牙裔服务的机构。这项工作将成为一名女研究生的博士论文。

Dr. Rand and graduate student Sharon Meidt will apply a new method to measure how fast the spiral and bar patterns of disk galaxies rotate about the galaxy center. These patterns are found in most disk galaxies, including our own Milky Way. Classical theories of spiral structure posit that an unstable disk of stars develops a set of growing modes, each with a fixed pattern speed. Structures with multiple pattern speeds, interpreted as coupled modes, have been seen in gravitational N-body simulations of galaxy disks; generally, the faster pattern dominates closer to the center. Dr Rand and collaborator Michael Merrifield have developed the 'modified Tremaine-Weinberg' method to test whether observed spiral galaxies also have multiple pattern speeds. This method will be applied to seven nearby spiral galaxies for which the velocity field has been well mapped in CO and neutral hydrogen gas. This method will directly measure of the pattern speed to test theoretical models for the formation of spiral structure, and to determine whether the spirals are winding up over time.The University of New Mexico is both a research university and a Hispanic-serving institution. The work will form the PhD thesis of a woman graduate student.