Observational Evidence for Hot Wind Impact on pc-scale in Low-luminosity Active Galactic Nucleus

TL;DR

This study presents observational evidence of hot winds in low-luminosity AGNs, showing how these winds impact circumnuclear gas and contribute to AGN feedback through detailed spectral analysis and simulations.

Contribution

It identifies new blueshifted emission lines indicating wind-shocked gas, advancing understanding of hot wind feedback mechanisms in low-luminosity AGNs.

Findings

Detection of blueshifted O/Ne emission lines indicating outflows

Hot wind impedes black hole accretion by exerting ram pressure

Evidence of wind-shocked circumnuclear gas from simulations

Abstract

Supermassive black holes in galaxies spend majority of their lifetime in the low-luminosity regime, powered by hot accretion flow. Strong winds launched from the hot accretion flow have the potential to play an important role in active galactic nuclei (AGN) feedback. Direct observational evidence for these hot winds with temperature around 10 keV, has been obtained through the detection of highly ionized iron emission lines with Doppler shifts in two prototypical low-luminosity AGNs, namely M81* and NGC 7213. In this work, we further identify blueshifted H-like O/Ne emission lines in the soft X-ray spectra of these two sources. These lines are interpreted to be associated with additional outflowing components possessing velocity around several $10^3$ km/s and lower temperature (~0.2-0.4 keV). Blue-shifted velocity and the X-ray intensity of these additional outflowing components are hard to be explained by previously detected hot wind freely propagating to larger radii. Through detailed numerical simulations, we find the newly detected blue-shifted emission lines would come from circumnuclear gas shock-heated by the hot wind instead. Hot wind can provide larger ram pressure force on the clumpy circumnuclear gas than the gravitational force from central black hole, effectively impeding the black hole accretion of gas. Our results provide strong evidences for the energy and momentum feedback by the hot AGN wind.