| Type 2 AGNs with Double-Peaked [O III] Lines: Narrow Line Region Kinematics or Merging Supermassive Black Hole Pairs? (2009) | |||||||||
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 sigmas, 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. We suggest that a considerable fraction of the sample could be binaries, but spatially resolved optical imaging, spectroscopy, radio or X-ray follow up are needed to draw firm conclusions.. Comment: submitted to ApJ, August 5, 2009; the full table 1 can be accessed at http://www.astro.princeton.edu/~xinliu/agn2dnl/table1.dat | |||||||||
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