REJECTION OF THE BINARY BROAD-LINE REGION INTERPRETATION OF DOUBLE-PEAKED EMISSION-LINES IN 3 ACTIVE GALACTIC NUCLEI

It has been suggested that the peculiar double-peaked Balmer lines of certain broad-line radio galaxies come from individual broad-line regi ons associated with the black holes of a supermassive binary. We conti nue to search for evidence of the radial velocity variations character istics of a double-lined spectroscopic binary that are required in suc h a model. After spectroscopic monitoring of three suitable candidates (Arp 102B, 3C 390.3, and 3C 332) spanning two decades, we find no suc h long-term systematic changes in radial velocity. A trend noticed by Gaskell in one of the Balmer-line peaks of 3C 390.3 before 1988 did no t continue after that year, invalidating his inferred orbital period a nd mass. Instead, we find lower limits on the plausible orbital period s that would require the assumed supermassive binaries in all three ob jects to have total masses in excess of 10(10) M.. In the case of 3C 3 90.3, the total binary mass must exceed 10(11) M. to satisfy additiona l observational constraints on the inclination angle. We argue that su ch large binary black hole masses are difficult to reconcile with othe r observations and with theory. In addition, there are peculiar proper ties of the line profiles and flux ratios in these objects that are no t explained by ordinary broad-line region cloud models. We therefore d oubt that the double-peaked line profiles of Arp 102B, 3C 390.3, and 3 C 332 arise in pairs of broad-line regions. Rather, they are much more likely to be intimately associated with single black holes. The recen t discoveries of transient but otherwise similar double-peaked emissio n lines in nearby active galactic nuclei bolster the view that double- peaked emission lines are commonly produced by a single compact source .