Can Warm Absorbers Be Driven by Ultra-fast Outflows?

Abstract

Abstract Warm absorbers (WAs) located approximately in the region of 1–1000 pc are common phenomena in many active galactic nuclei (AGNs). The driving mechanism of WAs is still under debate. Ultra-fast outflows (UFOs) that are launched very close to the central black hole are also frequently observed in AGNs. When UFOs move outward, they collide with the interstellar medium (ISM) gas. In this paper, we study the possibility that WAs can be generated by the interaction between ISM gas and the UFOs. We find that under some ISM gas conditions, WAs can be generated. However, the covering factor of WAs is much smaller than that given by observations. This indicates that other mechanisms should also be at work. We also find that the properties of the WAs mainly depend on the density of the ISM injected into the computational domain from the outer radial boundary (1000 pc). The higher the density of the ISM is, the higher the mass flux and kinetic power of the WAs will be. The kinetic power of the UFO-driven WAs is much less than 1% of the bolometric luminosity of the host AGNs. Therefore, the UFO-driven WAs might not contribute sufficient feedback to the host galaxy.