The Quasar Feedback Survey: Ionised Outflows in type 2 QSOs with MUSE data

We study ionised gas properties in a sample of 18 luminous (log L bol at least45 erg/s) obscured QSOs at 0.085<z<0.2 observed with VLT/MUSE as part of the multi-wavelength Quasar Feedback Survey (QFeedS) and with VLA at low- and high-resolution data. We compare the outflow-related quantities with values reported in the literature and investigate possible correlations between the outflows and other properties of the ionised gas such as the electron density. We adopt a non-parametric approach to characterise the ionised gas kinematics, traced by the [O III]5007 emission line, and use W 80 measured from the unresolved nuclear spectra as a threshold to identify outflow-dominated spaxels. A qualitative comparison between the radio and the W 80 maps shows that, in general, the peak of the radio coincides with the peak of the W 80. The [O III]5007 is used as a proxy for the ionised gas mass, and the outflow-related properties are obtained in two different ways: the global, which uses flux-weighted velocities and radii; and the peak, relying on radial profiles. We correct the [O III]5007 flux for extinction using the Balmer decrement. We take advantage of the MUSE sensitivity and use the [Ar IV]4711,4740 doublet, only observable in the integrated r=1.5'' spectra, to measure the electron density in each galaxy. We obtain 500<n e [cm-3] <27700, leading to 0.03 < out/ (M yr-1) < 4.17 and 39< kin/ [erg/s] <42. Our results emphasise the importance of accurate n e determination, leading to a difference of 1 dex in the outflow rates and kinetic powers. We observe a positive correlation between n e and V out, interpreted as compression of the gas at higher velocities. This correlation should be further investigated at other luminosity and redshift ranges, but it can inform future outflow simulation studies.