Title：The origin of the Broad Line Region in Active Galactic Nuclei
Speaker：Bozena Czerny, Research Fellow
Unit：Poland Copernicus Astronomical Center
Place：Physics Building 573, Haiyun Campus, Xiamen University
Abstract： Broad Emission lines are the most prominent features in the optical/UV spectra of active galaxies but the details of their formation are still under discussion. The difficulties lie in the assesment of the cloud dynamics: clouds have to be roughly in Keplerian motion, covering large fraction of the sky from the point of view of the nucleus, but rarely in the line of sight, and showing very large range of the ionization parameter of the emitting plasma. This points towards some kind of wind/failed wind, forming a two-phase medium. I will discuss in more detail two formation mechanisms: dust-driven failed wind and self-gravity driven disk disruption, and compare them with the observational constraints on the location of the Broad Line Region. I will also discuss the observed evolution of the line profiles, using as an example our results from the monitoring of a quasar HE 0435-4312, which points out that such evolution in most (many) cases is not related to the presence of the binary black hole in the nucleus.