Large-scale outflows in luminous QSOs revisited

Abstract

Context. Feedback from active galactic nuclei (AGN) is thought to play an important role in quenching star formation in galaxies. However, the efficiency with which AGN dissipate their radiative energy into the ambient medium remains strongly debated. Aims. Enormous observational efforts have been made to constrain the energetics of AGN feedback by mapping the kinematics of the ionized gas on kpc scale. We study how the observed kinematics and inferred energetics are affected by beam smearing of a bright unresolved narrow-line region (NLR) due to seeing. Methods. We re-analyse optical integral-field spectroscopy of a sample of twelve luminous unobscured quasi-stellar objects (QSOs) (0.4 < z < 0.7) previously presented in the literature. The point-spread function (PSF) for the observations is directly obtained from the light distribution of the broad Hβ line component. Therefore, we are able to compare the ionized gas kinematics and derived energetics of the total, truly spatially extended, and unresolved [O iii] emission. Results. We find that the spatially resolved [O iii] line width on kpc scales is significantly narrower than the one before PSF deblending. The extended NLRs (ENLRs) appear intrinsically offset from the QSO position or more elongated which can be interpreted in favour of a conical outflow on large scales while a spherical geometry cannot be ruled out for the unresolved NLR. We find that the kinetic power at 5 kpc distance based on a spherical model is reduced by two orders of magnitude for a conical outflow and one order of magnitude for the unresolved NLR after PSF deblending. This reduced kinetic power corresponds to only 0.01−0.1 per cent of the bolometric AGN luminosity. This is smaller than the 5−10% feedback efficiency required by some cosmological simulations to reproduce the massive galaxy population. The injected momentum fluxes are close or below the simple radiation-pressure limit L bol /c for the conical outflow model for the NLR and ENLR when beam smearing is considered. Conclusions. Integral-field spectroscopy is a powerful tool to investigate the energetics of AGN outflows, but the impact of beam smearing has to be taken into account in the high contrast regime of QSOs. For the majority of observations in the literature, this has not been addressed carefully so that the incidence and energetics of presumed kpc-scale AGN-driven outflows still remain an unsolved issue, from an observational perspective.

Jet-driven Galaxy-scale Gas Outflows in the Hyperluminous Quasar 3C 273

“…Interestingly, the relation by Sun et al (2017) for R KDR predicts larger sizes than the R ENLR at the high-luminosity end. As discussed in Husemann et al (2016) it is possible that Figure 5. A cartoon describing our proposed scenario to explain the unusual gas kinematics of 3C 273.…”

KASHz: No evidence for ionised outflows instantaneously suppressing star formation in moderate luminosity AGN at z ∼ 1.4–2.6

“…Although, in many of the studies, the most powerful outflows are thought to remove gas at a rate faster than it can be formed into stars, there are still considerable uncertainties in these mass outflow rate calculations due to uncertain spatial scales and the assumptions required to convert emission line luminosities into gas masses (e.g. Karouzos et al 2016;Villar-Martín et al 2016;Husemann et al 2016;Rose et al 2018;Harrison et al 2018). Measurements are more accurate for the most nearby sources (e.g.…”

Quasar-mode Feedback in Nearby Type 1 Quasars: Ubiquitous Kiloparsec-scale Outflows and Correlations with Black Hole Properties

“…Large-scale ionized gas outflows are powerful and ubiquitous in both Types 1 and 2 (Liu et al 2013a(Liu et al ,b, 2014. The properties of these higher-redshift systems depend on the details of the removal of unresolved emission (Husemann et al 2016), though clearly outflows are present in many cases.…”