Large-scale Dynamics of Winds Driven by Line Force from a Thin Accretion Disk

TL;DR

This study uses large-scale simulations to explore how winds driven by line force from thin accretion disks behave at large radii, revealing dependencies on black hole mass and luminosity, and explaining observed ultra-fast winds.

Contribution

It provides the first large-scale dynamical simulations of line-force driven winds, showing their properties depend on black hole mass and luminosity, and matching observed ultra-fast wind features.

Findings

Winds can escape from black holes with mass ≥10^7 M_sun at high luminosity.

Wind kinetic energy flux exceeds 1% of Eddington luminosity at 0.6 L_edd.

Line force driven winds explain observed ultra-fast winds in X-ray bands.

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 ($M_{BH}$) and accretion disk luminosity. When the accretion disk luminosity is $0.6L_{edd}$ ($L_{edd}$ being Eddington luminosity), independent of $M_{BH}$, the winds have kinetic energy flux exceeding $1\% L_{edd}$ and can escape from the black hole potential. For the case with the accretion disk luminosity equaling 0.3$L_{edd}$, the strength of the winds decreases with the decrease of $M_{BH}$. If $M_{BH}$ decreases from $10^9$ to $10^6$ solar mass ($M_\odot$), the winds kinetic energy flux decreases from $\sim 0.01 L_{edd}$ to $ \sim 10^{-6} L_{edd}$. In case of $M_{BH}\geq 10^7 M_\odot$, winds can escape from black hole potential. In the case of $M_{BH}=10^6 M_\odot$, the winds can not escape. We find that for the ultra-fast winds observed in hard X-ray bands (\citealt{Gofford et al. 2015}), the observed dependence of the mass flux and the kinetic energy flux on accretion disk 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.