Large-scale dynamics of winds driven by line force from a thin accretion disc

Abstract

ABSTRACT Winds play a significant role in active galactic nuclei feedback process. Previous simulations studying winds only focus on a small dynamical range. Therefore, it is unknown how far the winds can go and what the properties of the winds will be if they can move to large radii. We perform simulations to study the large-scale dynamics of winds driven by line force. We find that the properties of the winds depend on both black hole mass (MBH) and accretion disc luminosity. When the accretion disc luminosity is 0.6Ledd (Ledd being Eddington luminosity), independent of MBH, the winds have kinetic energy flux exceeding $1{{\ \rm per\ cent}} L_{\rm edd}$ and can escape from the black hole potential. For the case with the accretion disc luminosity equaling 0.3 Ledd, the strength of the winds decreases with the decrease of MBH. If MBH decreases from 109 to 106 solar mass (M⊙), the winds kinetic energy flux decreases from ∼0.01 Ledd to ∼10−6Ledd. In case of $M_{\rm BH}\ge 10^7 \, \mathrm{M}_\odot$, winds can escape from black hole potential. In the case of $M_{\rm BH}=10^6 \, \mathrm{M}_\odot$, the winds cannot escape. We find that for the ultra-fast winds observed in hard X-ray bands, the observed dependence of the mass flux and the kinetic energy flux on accretion disc luminosity can be well produced by line force driven winds model. We also find that the properties of the ultra-fast winds observed in soft X-ray bands can be explained by the line force driven winds model.