Lecture
This lecture covers the classification and statistics of active galactic nuclei (AGN) at low redshifts, focusing on Seyfert galaxies and Quasi-Stellar Objects. It delves into the unified AGN model, discussing the structure of supermassive black holes, accretion disks, and jets. The lecture also explores the variability of AGN across different wavelengths and the use of megamasers to probe the central regions of AGN. Additionally, it touches on the measurement of orbital motion in galaxies like NGC4258 and the recent advancements in time-delay cosmography to determine the Hubble constant.