发稿时间:2019-10-08浏览次数:10

USTC Astronomy Colloquium Series: 2019 Fall
Fast Inflow Directly Feeding Black Hole Accretion Disk in Quasars
周宏岩  教授
中国科学技术大学、中国极地研究中心
2019/10/08, 4:00pm , the 19th-floor Observatory Hall
Quasars are believed to be powered by accretion of interstellar matter onto a super-massive black hole (SMBH) therein. Most of the observed energy is released in an accretion disk of inspiraling gas surrounding the SMBH. An enormous amount of fueling material, up to several tens solar masses per year, is expected to be transported inwards and consumed in the end. However, basic questions remain unanswered as to whether and how the accretion disks are supplied with external gas, since no disk-feeding inflow has hitherto been observed clearly. I will talk about the detection of redshifted broad absorption lines of hydrogen and helium atoms in a sample of quasars. The lines show broad ranges of Doppler velocities that extend continuously from zero to redshifts as high as 5,000 km/s. Such velocities are comparable to freefall speeds close to the black hole, constraining the fastest infalling gas to within 10,000 gravitational radii of the SMBH. Extensive photoionization modelling yields a characteristic radial distance of the inflow of approximately 1,000 gravitational radii, possibly overlapping with the outer accretion disk. Our results present the first compelling evidence for the long-sought inflow directly feeding quasars’ accretion disks with external mass, likely originating from the dusty torus at a parsec scale. Our approach provides a new tool to probe the bulk of the so far elusive fueling inflows in quasars. Their studies may help address some of the fundamental questions concerning accretion physics, the onset and sustainment of quasar activity, and the SMBH growth at centers of most galaxies.
 周宏岩,中国科学技术大学天文学系教授、中国极地研究中心研究员、南极天文学科负责人。1989年毕业于中国科学技术大学。历任中国科学技术大学讲师、副教授,美国佛罗里达大学访问教授,德国马克斯-普朗克地外物理研究所洪堡学者。研究方向为黑洞物理、星系天文和太阳系外行星系统。迄今在国际刊物发表学术论文100余篇,被引用3000多次。代表性研究成果主要包括:发现黑洞引力辐射反冲第一个观测证据;首先提出可利用光学光谱和红外光变探测黑洞潮汐力瓦解吸积恒星;提出确定类星体外流方向的新思想,首次发现部分宽吸收线类星体中存在极向外流和高速内流等。