Gemini long-slit observations of luminous obscured quasars: Further evidence for an upper limit on the size of the narrow-line region

Kevin N. Hainline, Ryan C. Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska, Guilin Liu, Xin Liu

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Abstract

We examine the spatial extent of the narrow-line regions (NLRs) of a sample of 30 luminous obscured quasars at 0.4 < z < 0.7 observed with spatially resolved Gemini-N GMOS long-slit spectroscopy. Using the [O III] λ5007 emission feature, we estimate the size of the NLR using a cosmology-independent measurement: the radius where the surface brightness falls to 10-15 erg s-1 cm-2 arcsec-2. We then explore the effects of atmospheric seeing on NLR size measurements and conclude that direct measurements of the NLR size from observed profiles are too large by 0.1-0.2 dex on average, as compared to measurements made to best-fit Sérsic or Voigt profiles convolved with the seeing. These data, which span a full order of magnitude in IR luminosity (log (L8 μm/erg s-1) = 44.4-45.4), also provide strong evidence that there is a flattening of the relationship between NLR size and active galactic nucleus luminosity at a seeing-corrected size of ̃7 kpc. The objects in this sample have high luminosities which place them in a previously under-explored portion of the size-luminosity relationship. These results support the existence of a maximal size of the NLR around luminous quasars; beyond this size, there is either not enough gas or the gas is over-ionized and does not produce enough [O III] λ5007 emission.

Original languageEnglish (US)
Article number65
JournalAstrophysical Journal
Volume787
Issue number1
DOIs
StatePublished - May 20 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Cosmology: observations
  • galaxies: active
  • galaxies: evolution
  • galaxies: nuclei

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