Galaxy-scale ionised winds driven by ultra-fast outflows in two nearby quasars

TL;DR

This study investigates galaxy-scale ionised winds driven by ultra-fast outflows in two nearby quasars, revealing their properties, dynamics, and the underlying wind-driving mechanisms, and comparing them with theoretical models and other quasars.

Contribution

It provides detailed observational analysis of ionised outflows in two quasars with UFOs, supporting the momentum-driven wind scenario and constraining wind energetics.

Findings

Ionised outflows extend up to a few kpc with high velocity dispersion (~800 km/s).

Mass outflow rates reach a few solar masses per year, with kinetic efficiencies of 0.1-0.4%.

Winds are consistent with either momentum-driven or energy-driven regimes, with implications for AGN feedback.

Abstract

We use MUSE adaptive optics (AO) data in Narrow Field Mode to study the properties of the ionised gas in MR 2251-178 and PG 1126-041, two nearby (z~0.06) bright quasars hosting sub-pc scale Ultra Fast Outflows (UFOs) detected in the X-ray band. We decompose the optical emission from diffuse gas into a low- and a high-velocity components. The former is characterised by a clean, regular velocity field and a low (~80 km/s) velocity dispersion. It traces regularly rotating gas in PG 1126-041, while in MR 2251-178 it is possibly associated to tidal debris from a recent merger or flyby. The other component is found to be extended up to a few kpc from the nuclei, and shows a high (~800 km/s) velocity dispersion and a blue-shifted mean velocity, as expected from AGN-driven outflows. We estimate mass outflow rates up to a few Mo/yr and kinetic efficiencies between 0.1-0.4 per cent, in line with those of galaxies hosting AGNs of similar luminosity. The momentum rates of these ionised outflows are comparable to those measured for the UFOs at sub-pc scales, consistent with a momentum-driven wind propagation. Pure energy-driven winds are excluded unless about 100x additional momentum is locked in massive molecular winds. By comparing the outflow properties of our sources with those of a small sample of well-studied QSOs hosting UFOs from the literature, we find that winds seem to systematically lie either in a momentum-driven or in an energy-driven regime, indicating that these two theoretical models bracket very well the physics of AGN-driven winds.