Double-Peaked Narrow-Line Active Galactic Nuclei. II. The Case Of Equal Peaks

Active galactic nuclei (AGNs) with double-peaked narrow lines (DPAGNs) may be caused by kiloparsec-scale binary AGNs, bipolar outflows, or rotating gaseous disks. We examine the class of DPAGNs 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 DPAGNs from Smith et al., the "equal-peaked" objects (EPAGNs) have [Ne V]/[O III] ratios lower than for a control sample of non-double-peaked AGNs. This is unexpected for a pair of normal AGNs 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.University Cooperative Society of the University of Texas at AustinJane and Roland Blumberg Cenntenial Professorship in AstronomyAlfred P. Sloan FoundationNational Aeronautics and Space AdministrationNational Science FoundationU.S. Department of EnergyJapanese MonbukagakushoMax Planck SocietyUniversity of ChicagoInstitute for Advanced StudyJapan Participation GroupJohns Hopkins UniversityKorean Scientist GroupLos Alamos National LaboratoryMax-Planck-Institute for Astronomy (MPIA)Max-Planck-Institute for Astrophysics (MPA)New Mexico State UniversityUniversity of PittsburghUniversity of PortsmouthPrinceton UniversityUnited States Naval ObservatoryUniversity of WashingtonFermilabAstronom