报告题目：Black Holes Grow More Efficiently in Massive Galaxies

　　主讲人：杨光

　　报告人简介：杨光是美国宾夕法尼亚州立大学天文系在读博士生，他的博士生导师是Niel Brandt教授，是该校Verne M. Willaman冠名教授、2016年度美国天文学会高能天体物理最高奖Bruno Rossi奖获得者，主要从事活动星系核和Chandra X射线天文台巡天观测。杨光本科毕业于中国科学技术大学，本科阶段在中国科大天文系薛永泉教授课题组就发表了一篇第一作者的ApJS文章。

　　报告摘要：The potential coevolution between supermassive black holes (SMBHs) and their host galaxies remains a fundamental problem.In the local universe, the proportionality between SMBH mass and stellar mass of host galaxies provides a strong support for coevolution. Observations of distant star-forming galaxies reveal a tight linear correlation between star formation rate (SFR) and sample-average black-hole accretion rate (BHAR). However, for the host galaxies of X-ray selected AGNs, the SFR is flat as a function of BHAR except at high X-ray luminosities. To reconcile the apparent discrepancy, a recent study advanced a coevolution model assuming that SFR is proportional to long-term average BHAR (average over ~100 Myr), but shorter-term variability has obscured the BHAR-SFR relation.This model is capable in explaining almost all the observational facts so far. We verify this simple coevolution scenario by studying BHAR dependence on SFR and stellar mass (M_*) of host galaxies. Our study is based on the 7 Ms Chandra Deep Field-South (CDF-S) survey, the deepest X-ray survey, which is available recently. We find that SFR alone is not an adequate tracer of long-term average BHAR. Massive galaxies (M_*>10^10 M_sun) have higher ratios of BHAR/SFR than their less-massive counterparts, indicating that their SMBHs grow more efficiently.

　　时间：12月20日 (周二) 下午14:00-16:00

　　地点：紫台办公大楼416会议室

　　联系人：孙玮 (83332162), 冯磊 (83332180)