Reinvestigation of the unified theory for Seyfert galaxies by observing water vapor masers

(1)新建地测所筑波32 m望远镜20 ghz波段观测系统，对Seyfert星系核区水汽脉泽发射进行观测。该望远镜在22 GHz时的HPBW为100”，主波束效率和孔径效率分别为0.52和0.40，接收机前端为HEMT放大器，冷却温度为20 K，灵敏度为19.5 ~ 25.2 GHz。中间频率为4 ~ 8ghz。一台光谱仪为傅立叶变换型数字光谱仪，频段为1 GHz，通道数为16 k，系统噪声温度包括大气和欧姆损耗在天顶为60-80 k。该系统可用于观测塞弗特星系的水蒸气脉泽辐射，从而研究塞弗特星系的核区。我们开始监测来自塞弗特星系的水脉泽的速度。此外，我们还发现2型Seyfert星系中心的脉泽盘IC 1481很厚，质量很大，这证实了我们的假设，即1型和2型Seyfert星系之间的差异不仅是由吸积盘的视角造成的，而且是由吸积盘的厚度造成的。

(1) The 20-GHz band observing system of the Tsukuba 32-m telescope of the Geographical Survey Institute was newly constructed to make observations of water-vapor maser emission in the nuclear regions of Seyfert galaxies. The HPBW of the telescope was 100" at 22 GHz, and the main beam efficiency and the aperture efficiency were 0.52 and 0.40, respectively The receiver frontend was a HEMT amplifier cooled at 20 K and had sensitivity at the radio frequencies of 19.5 - 25.2 GHz. The intermediate frequencies were 4 - 8 GHz. A spectrometer was the Fourier transformation-type digital spectrometer with the frequency band of 1 GHz and the channel number of 16 k. The system noise temperature including the atmosphere and ohmic loss was 60-80 K at the zenith. The system is useful to study the nuclear regions of Seyfert galaxies by observing water-vapor maser emission.(2) We started monitoring observations of velocities of water masers from Seyfert galaxies. In addition, we revealed that a maser disk at the center of a type 2 Seyfert, IC 1481, was thick and massive, confirming our hypothesis in which the difference between the type 1 and 2 of Seyfert galaxies is caused by not only the viewing angle of the accretion disk but also the thickness of the disk.