### Question --- What are “active galactic nuclei”? What is the “unified model of AGN”, and how does it explain the variety of AGN that are observed? How and when are AGN important for galaxy evolution? ### Answer --- ##### What are “active galactic nuclei”? ![[Active Galactic Nuclei#General Information]] ##### What is the “unified model of AGN”, and how does it explain the variety of AGN that are observed? ![[Active Galactic Nuclei#Unified AGN Model]] ![[Active Galactic Nuclei#^agn-schematic]] ##### How and when are AGN important for galaxy evolution? As mentioned in [[Question 108]], it inhibits star formation in large galaxies by heating the gas and preventing collapse. ![[schechter_luminosity_function_comparison.png|align:center]]