Vega碎片盘的结构特性研究

A Study on the Characteristics of the Structure of Vega's Debris Disk

Vega的碎片盘在早期的观测中出现特殊结构,这可能是其内部存在潜在的高偏心率行星导致的.但是,近期对Vega的多波段高分辨率观测显示,Vega的碎片盘是一个平滑的盘结构,这虽然不能否定其内部存在行星的假说,但是对其中潜在行星的某些轨道参数提供了限制条件.使用数值模拟的方法对Vega系统的碎片盘和可能存在的行星进行模拟.模拟中碎片盘位于80～120 AU.盘中尘埃尺寸为10～100μm,轨道偏心率与倾角都非常小.通过多组计算的结果发现,如果Vega系统中不存在行星,那么其碎片盘演化结果与最新的观测结果吻合得较好;如果存在行星,且行星偏心率较大(比如e=0.6)时,那么行星的轨道半长径不能大于60 AU,否则碎片盘会在行星的影响下产生明显的聚集现象.行星与碎片盘的2:1平运动共振是导致碎片盘产生结构的主要原因.

Clumpy structure in the Vega＇s debris disk has been previously reported at millimeter wavelengths and attributed to the concentrations of dust grains trapped in reso nances with a potential planet. However, current imaging at multiwavelengths with higher sensitivity is against the former observed structure. The disk is now revealed to have a smooth structure. A planet orbiting Vega could not be neglected, but the presentday ob servations may place a severe constraint on the orbital parameters for the potential planet. Herein, we utilize modified MERCURY codes to numerically simulate Vega system, consist ing of debris disk and a planet. In our simulations, the initial inner and outer boundaries of the debris disk are assumed to be 80 AU and 120 AU, respectively. The radius of dust grains distributes in the range from 10 ttm to 100 ttm, in nearly coplanar orbits. From the outcomes, we show that the evolution of debris disk is consistent with recent observations, if there is no planet orbiting Vega. However, if Vega owns a planet with a high eccentricity （e.g., e 0.6）, the planetary semimajor axis cannot be larger than 60 AU, otherwise, the structure of debris disk will congregate due to the existence of the postulated planet. The 2：1 mean motion resonances may play a significant role in sculpting the debris disk.