基于源频相位参考技术的低光度活动星系核的毫米波VLBI观测研究

源频相位参考（SFPR）技术是甚长基线干涉测量（VLBI）的新技术，它能延长毫米波观测的相干积分时间，提高VLBI观测的灵敏度。我们提出利用SFPR技术实现低光度活动星系核（LLAGN）的毫米波VLBI观测研究。有望将处于传统VLBI技术探测灵敏度边缘的LLAGN按照正常活动星系核成图和模型拟合分析，为深入研究LLAGN的中央核尺寸和亮温度等提供了可能；并且SFPR技术能同时测量LLAGN的核移，为研究其喷流结构形态和磁场强度提供了高精度测量数据。目前我们已经获得美国VLBA两个历元共24小时的观测时间，覆盖4个观测频段（8.8/22/44/88GHz），主要用于LLAGN的SFPR观测，为开展相关研究提供了条件保障。SFPR技术也可作为将来VLBI的发展趋势——多频同时接收观测系统的校准技术，具有重要的技术参考和科学应用价值。

Source-frequency phase-referencing (SFPR) technique is a new very long baseline interferometry (VLBI) technique. It can increase the coherent integration time and improve the sensitivity of millimeter VLBI observations. We propose to use SFPR technique for millimeter VLBI study of the low-luminosity active galactic nuclei (LLAGN). It is hoped to have the LLAGN, which is near the detection edge of traditional VLBI technique, being imaged and model-fitted as a normal active galactic nuclei. This provides an opportunity to study the core size and brightness temperature of LLAGNs. Furthermore, SFPR can measure the core-shift of LLAGNs, which reflects the morphology and magnetic field along the jet precisely. We have obtained two epochs observation time on LLAGN (24 hours in total) with VLBA in SFPR mode, it covers four frequency bands including 8.8, 22, 44 and 88GHz. This guarantees a full understand of SFPR technique with these experiments. SFPR can also serve for the calibration of future simultaneous multi-band VLBI receiving system. The study of this program pave a way to the related technique and scientific applications.