Can warm absorbers be driven by ultra-fast outflows?

TL;DR

This study investigates whether ultra-fast outflows can generate warm absorbers in active galactic nuclei through interactions with interstellar medium gas, finding some conditions that produce WAs but with limited coverage and feedback.

Contribution

It demonstrates that UFO-ISM interactions can generate WAs, but other mechanisms are likely needed to explain observed properties and feedback effects.

Findings

WAs can be generated by UFO-ISM interactions under certain conditions

The covering factor of UFO-driven WAs is smaller than observed

The kinetic power of UFO-driven WAs is less than 1% of AGN bolometric luminosity

Abstract

Warm absorbers (WAs) located approximately in the region of $1-1000$ parsecs are common phenomena in many active galactic nuclei (AGNs). The driving mechanism of WAs is still under debate. Ultra-fast outflows (UFOs) which are launched very close to the central black hole are also frequently observed in AGNs. When UFOs move outwards, they will collide with the interstellar medius (ISM) gas. In this paper, we study the possibility that whether 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 parsec). 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 its host AGNs. Therefore, the UFO driven WAs might not contribute sufficient feedback to its host galaxy.