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Observational and theoretical studies of high-velocity components of extragalactic water masers

河外水脉泽高速分量的观测与理论研究

基本信息

批准号：
05640317
负责人：
DEGUCHI Shuji
金额：
$ 1.47万
依托单位：
National Astronomical Observatory
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05640317/
关键词：
maser water active galaxy accretion disk Raman scattering 水メーザー系外銀河

项目摘要

In 1992, water masers in NGC4258 was discoverd to exhibit extreme high velocity features of about 1000km/s, which is much larger than the outflow velocity of normal water masers. For the explanation of this phenomena, we have studied the models of masers from a rotating disk around the galactic nucleus, or models of the frequncy shift due to Raman scattering, both observationally and theoretically. First, we have investigated the model of Raman scattering in plasma and found what conditions are required for the density and temperature of the plasma (Deguchi 1994). It was predicted in this paper that, if this model is correct, emission from extreme high velocity components in NGC4258 is slightly polarized. We have performed the polarization observationswith the 37m radio telescope at Haystack, U.S.A.It has turned out in two sessions of observations that the degree of linear polarization is less than 20% (Deguchi 1995). This reult indicates that the linear polarization disappears due to the Farady depolarization in the strong magnetic field. Miyoshi et al. (1995) have performed position measurements of extreme velocity components with U.S.Very Long Baseline Array and found that the extreme components come from the position by 3 milli-arcsec separated from the main components. Though Watson and Walin proposed a rotating disk model which can provide the condition between positions and velocities of spots, we have shown that the simple disk model have to add the warp motion of the disk rotation and it cannot explain the weakness of the blue -shifted feature. In addition, to investigate the general properties of astrophysiccal masers, we have investigated the pumping mechanism of masers (especially for the methanol masers) with Dr.A.M.Sobolev. We have also worked on the Raman scattering masers with Dr.R.T.Gangadhara in Indian Institute of Astrophysics.

1992年，NGC4258中的水脉泽被发现表现出约1000km/s的极高速度特征，远大于普通水脉脉的流出速度。为了解释这种现象，我们从观测和理论上研究了围绕银河核旋转的圆盘的微波激射模型，或拉曼散射引起的频移模型。首先，我们研究了等离子体中的拉曼散射模型，并找到了等离子体的密度和温度所需的条件（Deguchi 1994）。本文预测，如果该模型正确，NGC4258 中极高速组件的发射会出现轻微偏振。我们用美国Haystack的37m射电望远镜进行了偏振观测，两次观测表明线偏振度小于20%（Deguchi 1995）。该结果表明，由于强磁场中的法拉第去极化，线性极化消失。三吉等人。 (1995)用美国甚长基线阵列对极端速度分量进行了位置测量，发现极端分量来自于与主要分量相距3毫角秒的位置。虽然Watson和Walin提出了一个旋转盘模型可以提供光点位置和速度之间的条件，但我们已经证明简单的盘模型必须添加盘旋转的扭曲运动，并且它不能解释蓝移特征的弱点。此外，为了研究天体物理脉射器的一般特性，我们与A.M.Sobolev博士一起研究了脉射器（特别是甲醇脉射器）的泵浦机制。我们还与印度天体物理研究所的 R.T.Gangadhara 博士一起研究了拉曼散射脉泽。