Quest on Yong Radio Galaxies Using Space-VLBI

我们的目标是通过对年轻射电星系的光谱和大小的观测，对它们的环境进行统计研究。自由-自由吸收（FFA）过程被用作探测围绕着射电星系的冷致密等离子体。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的核心周围发现了一个1倍等离子体环，这是我们的样本之一。FFA向细胞核方向最大。测得的电子密度和温度分别为2.5 × 10^4（小于等于）n_c（小于等于）2.6 × 10^6 cm（<-3>）和10^4（小于等于）T_e（小于等于）4.9 × 10^6 K)。在向西退去的喷流上，不透明度在1%以上逐渐减少，而在向东逼近的喷流上，不透明度在0.1%左右减少。朝向西部喷流的不透明区域与H_2O脉泽斑点重合。脉泽的速度梯度表明环面内的分子以~ 200 km s^<-1>的速度吸积到原子核。这些结果见karneo et al. 2003， PASA, 20, press No.1。我们对18个年轻的射电星系进行了五色调查，发现年轻的射电星系和类星体在FFA不透明度的分布方面存在显著差异。虽然年轻的射电星系倾向于显示对称的双叶FFA不透明，但年轻类星体的不透明是不对称的。这种明显的差异可以用统一方案来解释（Barthel 1989, ApJ, 336, 606），该方案声称类星体和射电星系本质上是相同的，但在小角度和大角度上分别有明显的不同。小的观察角度会产生不同的光路长度，穿过叶周围的冷致密等离子体，从而导致不对称的FFA不透明。结果报告已提交给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.