Warped discs and the directional stability of jets in active galactic nuclei

摘要: Warped accretion discs in active galactic nuclei (AGN) exert a torque on the black hole that tends to align rotation axis with angular momentum of outer disc. We compute magnitude this by solving numerically for steady-state shape warped disc, and verify analytic solution Scheuer & Feiler provides an excellent approximation. generalize these results strong warps arbitrary surface density profiles, calculate time-scale over which becomes aligned For massive holes rates order Eddington limit, alignment is always short (≲106 yr), so jets accelerated from inner disc region provide prompt tracer gas at large radii Longer time-scales are predicted low-luminosity systems, depending degree anisotropy hydrodynamic response shear warp, final decay modest potentially observable via very-long-baseline interferometry (VLBI). discuss implications inferred history those AGN jet directions appear be stable long time-scales. The energy deposition rate during rapid realignment episodes should make such objects transiently bright optical infrared wavelengths.