Similarity of ionized gas nebulae around unobscured and obscured quasars

Guilin Liu, Nadia L. Zakamska, Jenny E. Greene

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Quasar feedback is suspected to play a key role in the evolution of massive galaxies, by removing or reheating gas in quasar host galaxies and thus limiting the amount of star formation. In this paper, we continue our investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1) quasars, to determine the morphology and kinematics of ionized gas around these objects, predominantly via observations of the [O III] λ5007 Å emission line. We find that ionized gas nebulae extend out to ∼13 kpc from the quasar, that they are smooth and round, and that their kinematics are inconsistent with gas in dynamical equilibrium with the host galaxy. The observed morphological and kinematic properties are strikingly similar to those of ionized gas around obscured (type 2) quasars with matched [O III] luminosity, with marginal evidence that nebulae around unobscured quasars are slightly more compact. Therefore, in samples of obscured and unobscured quasars carefully matched in [O III] luminosity, we find support for the standard geometry-based unification model of active galactic nuclei, in that the intrinsic properties of the quasars, of their hosts and of their ionized gas appear to be very similar. Given the apparent ubiquity of extended ionized regions, we are forced to conclude that either the quasar is at least partially illuminating pre-existing gas or that both samples of quasars are seen during advanced stages of quasar feedback. In the latter case, we may be biased by our [O III]-based selection against quasars in the early 'blow-out' phase, for example due to dust obscuration.

Original languageEnglish (US)
Pages (from-to)1303-1318
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Jun 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: ISM
  • Galaxies: formation
  • Galaxies: nuclei
  • Quasars: emission lines


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