黑洞与其弯曲吸积盘的排列和活动星系核的周期寿命
Alignments Of Black Holes With Their Warped Accretion Disks And Episodic Lifetimes Of Active Galactic Nuclei
摘要：
翘曲的吸积盘由于其在通过Bardeen-Petterson效应形成超大质量黑洞（SMBH）的自旋方面的关键作用而引起了广泛的关注，Bardeen-Petterson效应是一种广义相对论效应，导致黑洞和翘曲的吸积盘之间的最终对准或反对准。我们研究这样的对齐过程，明确考虑到有限大小的吸积盘和情节的生命周期的活动星系核描绘的气体燃料到吸积盘的持续时间。我们采用一个近似的全球模型来模拟吸积盘的演变，允许确定的重力磁力矩驱动的路线，在一个相当简单的方式。然后，我们追踪黑洞的质量和自旋的演化路径，无论是在一个单一的活动插曲，并在一系列的插曲。在各向同性随机注入气体的情况下，我们计算了不同寿命的自旋演化，发现自旋演化对寿命相当敏感。因此，我们建议，自旋分布的SMBH可以放置的活动星系核的幕式寿命的限制，反之亦然。应用我们的结果所观察到的自旋分布的SMBH和所观察到的情节寿命的活动星系核进行了讨论，虽然这两个测量目前还不明确，得出一个坚定的结论。我们的处方可以很容易地纳入半解析模型的黑洞的增长和自旋演化。
英文摘要：
Warped accretion disks have attracted intensive attention because of their critical role on shaping the spin of supermassive massive black holes (SMBHs) through the Bardeen-Petterson effect, a general relativistic effect that leads to final alignments or anti-alignments between black holes and warped accretion disks. We study such alignment processes by explicitly taking into account the finite sizes of accretion disks and the episodic lifetimes of AGNs that delineate the duration of gas fueling onto accretion disks. We employ an approximate global model to simulate the evolution of accretion disks, allowing to determine the gravitomagnetic torque that drives the alignments in a quite simple way. We then track down the evolutionary paths for mass and spin of black holes both in a single activity episode and over a series of episodes. Given with randomly and isotropically oriented gas fueling over episodes, we calculate the spin evolution with different episodic lifetimes and find that it is quite sensitive to the lifetimes. We therefore propose that spin distribution of SMBHs can place constraints on the episodic lifetimes of AGNs and vice versa. Applications of our results on the observed spin distributions of SMBHs and the observed episodic lifetimes of AGNs are discussed, although both the measurements at present are yet ambiguous to draw a firm conclusion. Our prescription can be easily incorporated into semi-analytic models for black hole growth and spin evolution.
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