Lecturer: Prof. Ari Laor Affiliation: Technion - Israel Institute of Technology Abstract: Photoionization models include the transfer of energy from the radiation to the illuminated matter, but often neglect the momentum transfer. This momentum transfer can determine the density structure of the photoionized gas, leading to a single solution. I will discuss the implications of this effect to the observed emission and absorption properties of Active Galactic Nuclei, and it’s possible relevance to various other systems. Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.lf7kiulbf17mknvig8mgjbf67s&hs=121