TYPE 2 ACTIVE GALACTIC NUCLEI WITH DOUBLE-PEAKED [O III] LINES: NARROW-LINE REGION KINEMATICS OR MERGING SUPERMASSIVE BLACK HOLE PAIRS?
- Department of Astrophysical Sciences, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States)
We present a sample of 167 type 2 active galactic nuclei (AGNs) with double-peaked [O III] lambdalambda4959,5007 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 Hbeta 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{sup -1}, larger by a factor of approx1.5 than the line full width at half maximum of each component. The offset correlates with the host stellar velocity dispersion sigma{sub *}. The host galaxies of this sample show systematically larger sigma{sub *}, stellar masses, and concentrations, and older luminosity-weighted mean stellar ages than a regular type 2 AGN sample matched in redshift, [O III] lambda5007 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 follow-up are needed to draw firm conclusions.
- OSTI ID:
- 21392472
- Journal Information:
- Astrophysical Journal, Vol. 708, Issue 1; Other Information: DOI: 10.1088/0004-637X/708/1/427; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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