Institution(s): 1. Korea Institute for Advanced Study (KIAS)
Active Galactic Nuclei (AGN) have been considered as one of the most intriguing objects in the universe for huge amount of energy from their central part, Super Massive Black Hole (SMBH), and many interesting spectral features. There have been many studies on their mechanism, formation and evolution. To this end, looking at in which environment AGN live can help us. So far, it seems that AGN prefers intermediate density regions (galaxy groups) to dense region (galaxy clusters) from many studies with several different samples and methods. With the current largest catalogs of quasars and galaxies provided by SDSS, we construct a galaxy number density field as background density and assign it to quasars. Then we study the relation between background density and quasar density, and how quasar characteristics such as black hole mass and Eddington ratio change in different background density levels. We find that quasars are everywhere even in underdense regions, and proportion between background density and quasar density increases as goes to underdense regions. The physical properties also change with environment.