Institute of Astronomy

Stellar rejuvenation around massive black holes in the Galactic center and metal-rich quasars, and gravitational wave sources in AGN disks: Analog of planetary systems around massive black holes

SpeakerTalk DateTalk Series
Douglas N. C. Lin (University of California, Santa Cruz)10 May 2018Institute of Astronomy Colloquia


The prevalence of massive black holes and nuclear stellar clusters implies some stars may be trapped in accretion disks around active galactic nuclei.  We determine the star trapping rate and we show that the trapped stars rapidly accrete gas which leads to a top heavy initial mass function similar to that found in the Galactic Center. These massive stars undergo supernova explosion, pollute the accretion disks around high-redshift quasars to produce super solar metallicity. They also produce single stellar-mass black hole remnants which gain mass through accretion and capture companions.  Binary seed black holes lose angular momentum to the surrounding gas to tighten their separation.  They generate intense gravitational wave when they coalesce. We provide analysis on the distribution of their masses, mass ratio, spin rate, binary orbit-spin obliquity and red-shift-dependent occurrence rate as observable predictions. I will describe some relevant mechanisms which are analogous to the astrophysics of planet formation and the implications of this scenario in the context of 1) coeval population and kinematic properties of disk and S stars around the Galactic center,  2) super solar metallicity, 3) duty cycle of AGN active phase, and 4) the rapid growth of their central massive black holes. 


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