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arXiv · 0908.2426

Type 2 AGNs with Double-Peaked [O III] Lines: Narrow Line Region Kinematics or Merging Supermassive Black Hole Pairs?

Xin Liu·Yue Shen·Michael A. Strauss·Jenny E. Greene
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Abstract

We present a sample of 167 type 2 AGNs with double-peaked [O III] 4959,5007 narrow emission lines, selected from the Seventh Data Release of the Sloan Digital Sky Survey. The double-peaked profiles can be well modeled by two velocity components, blueshifted and redshifted from the systemic velocity. Half of these objects have a more prominent redshifted component. In cases where the H-beta emission line is strong, it also shows two velocity components whose line-of-sight (LOS) velocity offsets are consistent with those of [O III]. The relative LOS velocity offset between the two components is typically a few hundred km/s, larger by a factor of ~ 1.5 than the line full width at half maximum of each component. The offset correlates with the host stellar velocity dispersion sigma*. The host galaxies of this sample show systematically larger sigma*, stellar masses, and concentrations, and older luminosity-weighted mean stellar ages than a regular type 2 AGN sample matched in redshift, [O III] 5007 equivalent width and luminosity; they show no significant difference in radio properties. These double-peaked features could be due to narrow-line region kinematics, or binary black holes. The statistical properties do not show strong preference for or against either scenario, and spatially resolved optical imaging, spectroscopy, radio or X-ray followup are needed to draw firm conclusions.

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Xin Liu, Yue Shen, Michael A. Strauss, Jenny E. Greene. 2009-08-17. Type 2 AGNs with Double-Peaked [O III] Lines: Narrow Line Region Kinematics or Merging Supermassive Black Hole Pairs?. https://doi.org/10.1088/0004-637x/708/1/427

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