Phase Mixing in Stellar Systems and the Nucleus of M31

AST-9900316恒星系统中的相位混合和M31的核。特里梅因正在研究星系和星星团等恒星系统动力学的两个方面。 第一个是相混合，这是一个恒星系统的无碰撞等离子体达到平衡的过程。相位混合是一个渐进的过程，在这个过程中，系统形成时的不规则性越来越紧密地包裹在许多轨道上，因此宏观上恒星系统变得越来越平滑。 这些不规则性的持久性导致了几个重要的影响进行了研究：引力盘和暗晕之间的耦合在星系的内部，这可能会旋转和扁平的内晕;增强松弛的星系中心附近，可能各向同性的恒星分布函数;和存在突出的未绑定结构的相空间分布的恒星。 第二个是偏心恒星盘的动力学，例如被认为存在于附近星系M31中心的恒星盘。 这样的圆盘可以在接近开普勒引力势的情况下自然产生，例如靠近被认为位于附近星系中心的大质量中心黑洞。 特里梅因博士正在研究接近开普勒势的轴对称恒星盘的稳定性和正常模式，以确定偏心恒星盘是否自然产生并持续到星系的年龄。

AST-9900316Phase mixing in stellar systems and the nucleus of M31Scott TremaineDr. Tremaine is studying two aspects of the dynamics of systems of stars such as galaxies and star clusters. The first is phase mixing, the process by which a stellar system of collisionless plasma reaches equilibrium. Phase mixing is a gradual process, in which irregularities present at the formation of the system become more and more tightly wrapped over many orbits so that macroscopically the stellar system becomes smoother and smoother. The persistence of these irregularities leads to several important effects that are investigated: gravitational coupling between the disk and dark halo in the inner parts of galaxies, that may spin up and flatten the inner halo; enhanced relaxation near the centers of galaxies that may isotropize the stellar distribution function; and the presence of prominent unbound structures in the phase space distribution of stars. The second is the dynamics of eccentric stellar disks such as the one believed to be present in the center of the nearby galaxy M31. Such disks can arise naturally in a nearly Keplerian gravitational potential, for example close to the massive central black hole that is believed to sit in the centers of nearby galaxies. Dr. Tremaine is studying the stability and normal modes of axisymmetric stellar disks in nearly Keplerian potentials, to determine whether eccentric stellar disks arise naturally and persist for the age of the galaxy.