Yan-Rong Li, Jian-Min Wang, Cheng Cheng, Jie Qiu
We investigate the aligment processes between spinning black holes and warped accretion disks around them in a frame of two different types of feeding at the outer boundaries. We consider: I) fixed flows in which gas is continually fed with a preferred angular momentum, and II) free flows in which there is no gas supply and the disks diffuse freely at their outer edges. As expected, we find that for the cases of fixed flows the black hole-disk systems always end up alignments with timescales of several 10e6 years, irrespective of the initial inclinations. If the initial inclination angles larger than \pi/2, the black hole accretion transits from retrograde to prograde fashion and the accreted mass onto the holes during these two phases is comparable. On the other hand, for the cases of free flows, both alignments and anti-alignments can occur, depending on the initial inclinations and the ratios of the angular momentum of the disks to that of the holes. In such cases, the disks will be consumed within timescales of $10^6$ years by the black holes accreting at the Eddington limit. We propose that there is a close connect between black hole spins and the lifetimes that the feeding persists for, which determines the observable episodic lifetimes of active galactic nuclei. We conclude that careful inclusion of the feeding to the disks at the outer boundaries is crucial to modeling the evolution of black hole spins.
View original:
http://arxiv.org/abs/1212.2186
No comments:
Post a Comment