题  目：Measurements of Quasar Ages

　　报告人：Prof. Wei Zheng (Johns Hopkins University)

　　摘  要：What is the lifespan of these supermassive blackholes? I will start with a general introduction of the existing methods of quasar-age estimations, then present our recent results on the proximity profiles in the spectra of z ≈ 3 quasars, where fluxes extend blueward of the He ii Ly wavelength 304(1+z) A. Based on the HST spectra of He II quasars collected over two decades, we find a large difference in the proximity-zone sizes up to 20 Mpc in the source’s rest frame. With further modeling, we should in principle be able to estimate the quasar ages from their proximity sizes. Several special interesting cases will be discussed.

　　时  间：2015年4月28日（星期二）下午2：00

　　地  点：紫台办公大楼五楼会议室

　　联系人：马红君（83332210）

欢迎大家积极参加！

　　                                           紫金山天文台学术委员会