Quest on Yong Radio Galaxies Using Space-VLBI

我们通过观测年轻射电星系的光谱和大小，对它们的环境进行了统计研究。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。我们发现了一个围绕射电星系NGC1052核心的1-PC等离子体环，这是我们的样本之一。FFA不透明度向核标记最大值。测得的电子密度和温度分别为2.5×10^4[小于等于]nc[小于等于]2.6×10^6 cm^~(-3)和10^4[小于等于]T_e[小于或等于]4.9×10^6K。在1pC以上，不透明度沿西退急流逐渐减小，而从核心向东进射急流，不透明度在0.1pC时逐渐减小。向西喷流方向的不透明区域与H_2O脉泽斑所在的位置重合。脉泽的速度梯度表明，环内分子与原子核共生距离约200公里。这些结果发表在Karneno等人的文章中。我们对18个年轻射电星系的五色测量揭示了年轻射电星系和类星体在FFA不透明度分布方面的显著差异。年轻的射电星系倾向于向双叶方向显示对称的FFA不透明度，而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方案(Barthel 1989，APJ，336,606)来解释，该方案声称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明显不同。较小的视角会产生不同的路径长度，穿过围绕着波瓣的冷密等离子体，从而导致不对称的FFA不透明。有关结果的报告已提交给PASA。

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.