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

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Abstract
The impact of feedback from active supermassive black holes on their host galaxies is a key phenomenon in understanding galaxy evolution. We study ionised gas properties in a sample of 18 luminous (log L bol ≥ 45 erg s −1 ) obscured Quasi-stellar objects (QSOs) in the nearby Universe (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, 1″ and 0.3″ respectively. Our main goal is to characterise the disturbed gas kinematics in this galaxy sample. 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 Å 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 . [O III ] 5007 Å is used as a proxy for the ionised gas mass, and the outflow-related properties are obtained in two different ways: the global, using flux-weighted velocities and radii and the peak, which relies on radial profiles. We correct the [O III ] 5007 Å 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 ] < 27 700, leading to 0.03 < Ṁ out /[M ⊙ yr −1 ] < 4.17 and 39 < log Ė kin /[erg s −1 ] < 42. Our results emphasize the importance of accurate electron density 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.
Funding Information
  • United Kingdom Research and Innovation (UKRI2730)
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (303450/2022-3)
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (403398/2023-1)
  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (8887.894973/2023- 00)
  • Ministerio de Ciencia, Innovación y Universidades (JDC2023-052684-I)
  • Ministerio de Ciencia, Innovación y Universidades (PID2022−141105NB−I00)
  • Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (25/2551-0002765-9)
  • Istituto Nazionale di Astrofisica (CUP C59J2103472000)
  • ERC (101040227 - WINGS)

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