Key Laboratory of Particle Astrophysics;
Institute of High Energy Physics;
Chinese Academy of Sciences;
Beijing 100049;
China;
School of Astronomy and Space Science;
University of Chinese Academy of Sciences;
Beijing 100049;
China;
National Astronomical Observatories;
Chinese Academy of Sciences;
Beijing 100101;
China;
galaxies:active; quasars:supermassive black holes; gravitational waves;