Title: Hydrogen and Helium Absorption-Lines in Quasars

　　Speaker: 周宏岩 (中国极地研究中心)

　　Time:2:30 pm, January 10 (Thursday)

　　Location: Lecture Hall, 3rd floor

　　Abstract:

　　Being the most luminous steady objects known in the universe, quasars have been a long-standing enigma in modern astrophysics since their discovery. These cosmic beacons are believed to be powered by the gravitational potential energy of accreted matters released in the course of falling into a super-massive black hole. Their energetics and dynamics require massive in-/out-flows that may manifest themselves as broad absorption-lines (BALs) on quasar spectra. However, the commonly observed metal BALs of little diagnostic value in probing these flows of dense gas with high column densities at the heart of quasars, due to serious saturation and line blending effects. I will talk about a novel approach making use of BALs of hydrogen Balmer line series and of meta-stable natural helium line multiplets, including several case stories.