Warped accretion discs and the unification of active galactic nuclei

摘要: Orientation of parsec-scale accretion discs in active galactic nuclei (AGNs) is likely to be nearly random for different black hole feeding episodes. Because AGN are unstable self-gravity on parsec scales, star formation these will create young stellar discs, similar those recently discovered our Galactic Centre. The blend into the quasi-spherical cluster enveloping time-scales much longer than a lifetime. Therefore, gravitational potential within radius influence at best axisymmetric rather spherically symmetric. Here we show that, as result, newly formed disc warped. For simplest case resulting from thin ring, calculate precession rates, and time-dependent shape. We find realistic parameter range, becomes strongly warped few hundred orbital times. suggest that this, possibly other mechanisms warping, have direct relevance problem obscuration, masing narrow Fe Ka lines, etc.