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Quest on Yong Radio Galaxies Using Space-VLBI

利用太空-VLBI探索永射电星系

基本信息

批准号：
13640248
负责人：
KAMENO Seiji
金额：
$ 2.24万
依托单位：
National Astronomical Observatory of Japan
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640248/
关键词：
Active Galaxies Radio Galaxies Radio Interferometry Space-VLBI

项目摘要

We aimed a statistical study for environments of young radio galaxies via observations for their spectrum and size. Free-Free Absorption (FFA) process is used as a probe into cold dense plasma surrounding radio galaxies. Space-VLBI observations provides a sub-pc-scale resolution for the spatial distribution of the FFA opacities.We discovered a 1-pc plasma torus around the nucleus of a radio galaxy NGC 1052, which is one of our samples. The FFA opacity marks maximum towards the nucleus. The electron density and temperature measured 2.5 × 10^4【less than or equal】 n_c 【less than or equal】 2.6 × 10^6 cm^<-3> and 10^4 【less than or equal】 T_e 【less than or equal】 4.9 × 10^6 K, respectively. The opacity tapers along the western receding jet over 1 pc, while it is cut down at 0.1 pc from the nucleus to the eastern approaching jet. The opaque region towards the western jet coincides where H_2O maser spots are. The velocity gradient of masers indicates that molecules inside the torus accrete to the nucleus by 〜 200 km s^<-1>. These results are reported in Karneno et al. 2003, PASA, 20, No.1 in press.Our pentachromatic survey for 18 young radio galaxies revealed that significant difference between young radio galaxies and quasars, in terms of distribution of FFA opacities. While young radio galaxies tend to show symmetric FFA opacities towards double lobes, the opacities towards young quasars are asymmetric. The apparent difference can be explained by the unified scheme (Barthel 1989, ApJ, 336, 606), which claims that quasars and radio galaxies are intrinsically the same but apparently different by small and large viewing angles, respectively. A small viewing angle produces different path length through cold dense plasma surrounding the lobes and hence causes asymmetric FFA opacities. The report on the results was submitted to PASA.

我们的目的是通过观测年轻射电星系的光谱和大小，对它们的环境进行统计研究。自由-自由吸收（FFA）过程被用来探测射电星系周围的冷稠密等离子体。空间VLBI观测为FFA不透明度的空间分布提供了亚pc尺度的分辨率，我们在射电星系NGC 1052的核周围发现了一个1 pc等离子体环。FFA不透明标记朝向细胞核最大。测得的电子密度和温度分别为2.5 × 10^4[小于或等于] n_c [小于或等于] 2.6 × 10^6 cm^<-3>和10^4 [小于或等于] T_e [小于或等于] 4.9 × 10^6 K。不透明度沿着向西后退的急流逐渐变小，超过1个粒子，而从核到向东接近的急流，不透明度减少了0.1个粒子。向西喷流方向的不透明区与H_2O脉泽斑点的位置相吻合。脉泽的速度梯度表明，环内的分子以每秒10200公里的速度与核吸积<-1>。对18个年轻射电星系的五色巡天观测表明，年轻射电星系和类星体的FFA不透明度分布存在显著差异。年轻的射电星系倾向于对双瓣显示对称的FFA不透明度，而对年轻类星体的不透明度是不对称的。这种明显的差异可以用统一的理论来解释（Barthel 1989，ApJ，336，606），该理论认为类星体和射电星系本质上是相同的，但在小视角和大视角下却明显不同。小视角通过叶周围的冷致密等离子体产生不同的路径长度，从而导致不对称的FFA浑浊。结果报告已提交给PASA。