Magnetohydrodynamic winds driven by line force from the standard thin disk around supermassive black holes: II. a possible model for ultra-fast outflows in radio-loud AGNs

TL;DR

This paper develops a combined line-force and magnetic field model for ultra-fast outflows in radio-loud AGNs, supported by numerical simulations, to better explain observed UFO properties and their formation mechanisms.

Contribution

It introduces a hybrid wind model driven by both line force and magnetic fields, validated through numerical simulations, advancing understanding of UFOs in radio-loud AGNs.

Findings

Hybrid models better reproduce UFO properties than pure MHD models.

Magnetic fields stronger than gas pressure influence wind formation.

Simulations suggest combined forces are key to UFO acceleration.

Abstract

In radio-loud active galactic nuclei (AGNs), ultra-fast outflows (UFOs) were detected at the inclination angle of $\sim10^{\rm o}$--$70^{\rm o}$ away from jets. Except for the inclination angle of UFOs, the UFOs in radio-loud AGNs have similar properties to that in radio-quiet AGNs. The UFOs with such low inclination cannot be explained in the line-force mechanism. The magnetic-driving mechanism is suggested to explain the UFOs based on a self-similar solution with radiative transfer calculations. However, the energetics of self-similar solution need to be further confirmed based on numerical simulations. To understand the formation and acceleration of UFOs in radio-loud AGNs, this paper presents a model of the disk winds driven by both line force and magnetic field and implements numerical simulations. Initially, a magnetic field is set to 10 times stronger than the gas pressures at the disk surface. Simulation results imply that the disk winds driven by both line force and magnetic field could describe the properties of UFOs in radio-loud AGNs. Pure magnetohydrodynamics (MHDs) simulation is also implemented. When the initial conditions are the same, the hybrid models of magnetic fields and line force are more helpful to form UFOs than the pure MHD models. It is worth studying the case of a stronger magnetic field to confirm this result.