Double-Peaked Narrow Emission Lines in AGN: The Role of Rotating Disks
  AGN with double-peaked narrow lines (DPAGN) may be caused by kiloparsec scale
binary AGN, bipolar outflows, or rotating gaseous disks. We examine the class
of DPAGN in which the two narrow line components have closely similar intensity
as being especially likely to involve disks or jets. Two spectroscopic
indicators support this likelihood. For DPAGN from Smith et al. (2010), the
"equal-peaked" objects (EPAGN) have [Ne V]/[O III] ratios lower than for a
control sample of non-double peaked AGN. This is unexpected for a pair of
normal AGN in a galactic merger, but may be consistent with [O III] emission
from a rotating ring with relatively little gas at small radii. Also, [O
III]/H-beta ratios of the redshifted and blueshifted systems in the EPAGN are
more similar to each other than in a control sample, suggestive of a single
ionizing source and inconsistent with the binary interpretation.
