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Global Oscillations of Maser Disks in Active Glactic Nuclei and the Kinematics of Magamaser Sources

活动星系核中脉瑟盘的整体振荡和 Magamaser 源的运动学

基本信息

批准号：
09640324
负责人：
OKAZAKI Atsuo
金额：
$ 1.54万
依托单位：
Hokkai-Gakuen University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Recent discovery of water megamasers in circumnuclear regions of some type 2 active galactic nuclei (AGN) has opened a new way to probe the innermost parsec of the nuclei. The VLBI observations have revealed the detailed spatial and velocity distribution of the magemaser emission. Maser features in some AGN have been found to arise from geometrically thin, disk-like regions. Since such disks can be perturbed by global m = 1 oscillations, it is important to study the characteristics of these oscillation modes and their effects on the maser source kinematics. For this purpose, we have numerically studied the three dimensional distributions of the density and the velocity field in polytropic disks perturbed by the m =1 eigenmodes. The following is the summary of our results.1. Both z-symmetric (eccentric) modes and z-antisymmetric (warping) modes are present in magemaser disks, where z is the vertical coordinate. The perturbed velocity field associated with the warping mode is approximately vertical, whereas that associated with the eccentric mode is roughly horizontal.2. The model position-velocity diagram and velocity drift for maser disks perturbed by the warping mode are indistinguishable from those of Keplerian disks. This characteristic agrees well with the observed spatial and velocity distribution of the maser features of NGC 4258.3. In maser disks perturbed by the eccentric mode, the position-velocity diagram and the velocity drift become non-Keplerian. The observed sub-Keplerian line-of-sight velocity distribution of NGC 1068 can be attributed to this mode.

最近在一些2型活动星系核（AGN）的核周区域发现了水巨激子，为探测核最内层的秒差距开辟了一条新途径。VLBI观测揭示了磁激射发射的详细空间分布和速度分布。在一些AGN中发现脉泽特征是由几何上薄的盘状区域产生的。由于这样的圆盘可能受到全局m = 1振荡的扰动，因此研究这些振荡模式的特征及其对脉泽源运动学的影响是很重要的。为此，我们用数值方法研究了受m =1特征模态扰动的多向圆盘中密度场和速度场的三维分布。以下是我们研究结果的摘要。磁致激射盘中存在z-对称（偏心）模式和z-反对称（翘曲）模式，其中z为垂直坐标。翘曲模态的速度场近似垂直，偏心模态的速度场近似水平。受翘曲模式扰动的脉泽盘的模型位置-速度图和速度漂移与开普勒盘的模型位置-速度图和速度漂移难以区分。这一特征与观测到的NGC 4258.3脉泽特征的空间和速度分布非常吻合。在受偏心模式扰动的脉泽盘中，位置-速度图和速度漂移变成非开普勒的。观测到的NGC 1068的亚开普勒视线速度分布可以归因于这种模式。