Measuring Radially Varying Pattern Speeds in Spiral Galaxies

兰德博士和研究生莎伦·梅特将应用一种新方法来测量盘状星系的螺旋和条形图案绕星系中心旋转的速度。这些模式存在于大多数盘状星系中，包括我们所在的银河系。经典的螺旋结构理论假设，一个不稳定的恒星圆盘会发展出一套增长模式，每种模式都有固定的模式速度。具有多种模式速度的结构，被解释为耦合模式，已经在星系盘的引力N体模拟中看到；通常，更快的模式在更靠近中心的地方占主导地位。兰德博士和他的合作者迈克尔·梅里菲尔德开发了一种名为“改进的Tremaine-Weinberg”的方法来测试观测到的螺旋星系是否也具有多种模式的速度。这种方法将应用于附近的七个螺旋星系，这些星系的速度场在CO和中性氢气中已经得到了很好的映射。这种方法将直接测量模式的速度，以检验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卷曲。新墨西哥大学既是一所研究型大学，也是一所为拉美裔服务的机构。这项工作将形成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.